Free Online Paint Calculator

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Calculate the amount of paint needed for your project.

The longer side of the room
The shorter side of the room
Openings (Doors/Windows)
Total area for other openings

Paint Options
Filled in from the paint you choose. Type the value printed on your can to use it instead.

Trim and woodwork
Left empty: the room perimeter minus the door widths.
Typical baseboard and crown: 4-6 in (10-15 cm).
About 17 sq ft (1.6 m²) each. Left empty: the number of doors.
About 10 sq ft (0.9 m²) each. Left empty: the number of windows.

Trim enamel, semi-gloss or satin: 400-450 sq ft/gal (middle used).

Colors and preview
#D9CFC1
#F7F5F0
#FFFFFF
#3A4A5C
Room preview with the chosen colors

Build a palette from these colors
Your prices and labor (optional)
What a painter charges for each unit of surface. The total uses the surface to paint (walls, ceiling and trim).
Area one person paints in an hour, per coat. Leave empty to skip the time estimate.

Calculation Results

Area Summary

Gross Area
- sq ft
Openings
- sq ft
Net Area
- sq ft

Paint Needed

- gallons

10% waste included

Primer Needed

- gallons

Can Recommendation

Cost Estimate

Show calculation

    Project

    Tips

    Drying Time
    2-4 hours (touch dry), 24 hours (recoat)
    Application Tip
    Ensure surfaces are clean, dry, and dust-free before painting.

    Assumptions: coverage, texture, siding, stain and sprayer figures are the middle of the ranges in our paint guide below; they are typical values for one coat. The label on your paint can is the best guide, since brands differ.

    Paint Calculator: Estimate Paint Coverage, Costs & Gallons Needed

    A reliable paint calculator saves you from buying too much or too little paint for any project. Whether you’re refreshing a single room or tackling a whole-house painting project, knowing exactly how much paint to buy keeps you on budget and cuts down on extra trips to the store. This free paint calculator guide helps you estimate the gallons needed for interior design projects, exterior painting, ceilings, trim, and more.

    Just as architects carefully plan every element of a space, from bubble diagrams for spatial planning to final finishes, calculating paint quantities accurately ensures professional results without waste. This guide covers everything from basic formulas to cost estimates for DIY and professional painting projects. You’ll find interior paint calculator square feet breakdowns, an exterior paint estimator section, trim paint calculator tips, and much more.

    How to Calculate How Much Paint You Need

    The fundamental principle behind paint calculation is simple: measure the surface area you want to paint, then divide by the paint’s coverage rate. Accurate estimation requires accounting for doors, windows, number of coats, and surface texture. Tools like the Lowe’s paint estimator and the Sherwin-Williams paint calculator can help, but understanding the math yourself gives you a reliable backup.

    Paint calculator illustration showing room measurements for estimating paint coverage

    The Basic Paint Calculation Formula

    Gallons Needed = (Total Square Feet ÷ Coverage per Gallon) × Number of Coats

    Where:

    • Total Square Feet = Area to be painted minus doors and windows
    • Coverage per Gallon = Typically 350-400 sq ft for quality latex paint
    • Number of Coats = Usually 2 for best results

    Step-by-Step Paint Calculation

    1. Measure Your Walls

    Measure the length and height of each wall in feet. Multiply length × height to get the square footage of each wall. Add all walls together for total wall area.

    2. Subtract Doors and Windows

    Subtract non-paintable areas: Standard door ≈ 20 sq ft, Standard window ≈ 15 sq ft. This gives you the actual paintable surface area.

    3. Calculate Gallons Needed

    Divide the total paintable area by the paint’s coverage rate (check the can, typically 350-400 sq ft/gallon), then multiply by the number of coats.

    4. Add 10% for Waste

    Always round up and add a buffer for touch-ups, uneven surfaces, and small errors. It’s better to have a little extra than to run short mid-project.

    Example: Calculating Paint for a 12′ × 14′ Room

    • Room perimeter: (12 + 14) × 2 = 52 feet
    • Wall height: 8 feet
    • Total wall area: 52 × 8 = 416 sq ft
    • Subtract 1 door (20 sq ft) + 2 windows (30 sq ft) = 50 sq ft
    • Paintable area: 416 − 50 = 366 sq ft
    • At 375 sq ft/gallon coverage: 366 ÷ 375 = 0.98 gallons
    • For 2 coats: 0.98 × 2 = 1.96 gallons
    • Purchase: 2 gallons (accounts for touch-ups)

    Step-by-step paint calculation example for a 12x14 room

    Paint Coverage by Type

    Paint Type Coverage (sq ft/gallon) Best For
    Interior Latex Paint 350-400 Walls, ceilings, most interior surfaces
    Interior Primer 200-300 New drywall, color changes, stain blocking
    Exterior Latex Paint 250-350 Siding, trim, outdoor surfaces
    Exterior Primer 200-300 Bare wood, weathered surfaces
    Ceiling Paint 350-400 Ceilings, overhead surfaces
    Trim/Semi-Gloss 400-450 Baseboards, doors, molding
    Textured Paint 150-200 Texture finishes, specialty coatings

    Coverage rates vary by brand. Always check the manufacturer’s specifications. Premium paints from brands like Sherwin-Williams, Benjamin Moore, and Behr often provide better coverage than economy paints.

    Different paint types and their coverage rates comparison

    Lowe’s Paint Estimator vs. Brand Calculators

    Several retailers and manufacturers offer their own online paint estimators. The Lowe’s paint estimator is popular because it includes man-hours estimation alongside gallons needed. The Sherwin-Williams paint calculator lets you input custom room dimensions and offers quick presets. The Behr paint calculator covers interior, exterior, and stain estimates in one tool. Each calculator uses slightly different coverage assumptions, so cross-referencing two or three tools gives you a more reliable estimate. For the most accurate results, measure your rooms yourself and apply the formula above.

    Interior Paint Calculator

    Interior painting projects require careful planning to achieve professional results. Whether you’re beginning a home renovation or simply refreshing a room’s color palette, an accurate interior paint calculator saves both time and money. The key is measuring your walls in square feet and factoring in doors, windows, and coat count before heading to the store.

    Room-by-Room Paint Estimates

    Room Type Average Size Walls Only Walls + Ceiling
    Small Bathroom 40 sq ft floor 1 gallon 1.5 gallons
    Standard Bathroom 60 sq ft floor 1.5 gallons 2 gallons
    Small Bedroom 10′ × 10′ 1.5 gallons 2 gallons
    Standard Bedroom 12′ × 12′ 2 gallons 2.5 gallons
    Master Bedroom 14′ × 16′ 2.5 gallons 3.5 gallons
    Living Room 16′ × 20′ 3 gallons 4 gallons
    Kitchen 12′ × 14′ 2 gallons 2.5 gallons

    *Estimates assume 8-foot ceilings, 2 coats, and standard door/window deductions

    Interior Paint Calculator: Square Feet Breakdown

    To use an interior paint calculator based on square feet, follow this approach for any room shape. For a rectangular room, multiply the perimeter (sum of all wall lengths) by the ceiling height to get total wall square footage. Then subtract roughly 20 sq ft per door and 15 sq ft per window. A 10′ × 10′ room with 8-foot ceilings, one door, and one window works out to about 285 paintable square feet, requiring roughly 1.5 gallons for two coats. For L-shaped or irregular rooms, measure each wall segment individually, calculate them separately, and add the results together.

    Ceiling Paint Calculator

    Ceiling painting is straightforward since there are no doors or windows to subtract. Simply calculate the floor area:

    Ceiling Gallons = (Length × Width) ÷ Coverage × Coats
    Example: 14′ × 16′ Ceiling
    • Area: 14 × 16 = 224 sq ft
    • At 400 sq ft/gallon: 224 ÷ 400 = 0.56 gallons
    • For 2 coats: 0.56 × 2 = 1.12 gallons
    • Purchase: 1.5 gallons or 1 gallon + 2 quarts

    In the calculator, tick Include ceiling on the Room tab. The ceiling gets its own paint type, with ceiling paint (350 to 400 sq ft per gallon, calculated at 375) as the default, its own surface condition, and its own line under Paint Needed. For the same 14 × 16 ft room with 8 ft walls, two coats and the default 10% waste, the ceiling line is 1.32 gallons, bought as one gallon and two quarts, next to 2.47 gallons for the walls.

    Trim Paint Calculator

    Trim is measured in linear feet rather than square footage. A typical room has trim around the perimeter plus door and window casings. A dedicated trim paint calculator helps you avoid over- or under-buying.

    Trim Paint Formula:
    • Calculate total linear feet of trim
    • Multiply by trim width (typically 4-6 inches = 0.33-0.5 feet)
    • Add door casing area (approximately 17 sq ft per standard door)
    • Add window casing area (approximately 10 sq ft per standard window)
    • 1 gallon of trim paint covers approximately 150-200 linear feet

    The calculator above works trim out by area rather than by linear feet. Open Trim and woodwork and tick Calculate trim paint: it multiplies the baseboard and crown molding length by the trim width (5 inches unless you change it), adds about 17 sq ft per door casing and 10 sq ft per window casing, counts both faces of any door leaves you enter, and divides by 425 sq ft per gallon for semi-gloss or satin trim enamel, with your number of coats and waste allowance. Leave the baseboard length empty and it uses the room perimeter minus the door widths.
    For a standard 12′ × 14′ room with baseboards, crown molding, one door, and two windows, expect to need roughly 1 quart to 1 gallon of trim paint depending on trim width and number of coats. Semi-gloss or satin finishes are preferred for trim because they resist scuffs and wipe clean easily.

    Pro Tip: Semi-gloss or satin finishes are ideal for trim because they’re more durable and easier to clean than flat paint. Learn more about interior design concepts to choose the right finishes for your space.

    Interior paint calculator guide showing room measurements and gallon estimates

    Exterior Paint Calculator

    Exterior painting requires different considerations than interior work. Weather exposure, surface porosity, and architectural details all affect paint needs. A good exterior paint estimator accounts for siding type, gable areas, and window/door deductions. Proper planning is essential, just as understanding renovation costs helps budget effectively.

    Calculating Exterior Wall Area

    For exterior painting, measure each wall separately and account for gables, dormers, and other architectural features:

    1. Measure Rectangular Walls

    Length × Height for each wall section. For two-story homes, measure each floor separately.

    2. Calculate Gable Areas

    For triangular gables: (Base × Height) ÷ 2. Add this to your wall measurements.

    3. Subtract Openings

    Subtract windows (15-20 sq ft each), doors (20 sq ft each), and garage doors (120-160 sq ft).

    Exterior paint estimator diagram showing how to measure house walls and gables

    Exterior Paint Coverage by Siding Type

    Siding Type Coverage (sq ft/gal) Notes
    Smooth Wood 350-400 Standard coverage, may need primer
    Rough-Cut Wood/Cedar 200-300 Absorbs more paint, extra coats often needed
    Vinyl Siding 300-400 Requires special vinyl-safe paint
    Aluminum Siding 300-350 Needs proper primer for adhesion
    Stucco 150-250 Very porous, requires more paint
    Brick 100-150 Highly porous, requires primer and extra coats
    Concrete/Masonry 150-200 Requires masonry primer

    House Size Paint Estimates

    Home Size Exterior Sq Ft* Body Paint (gal) Trim Paint (gal)
    1,000 sq ft (1 story) ~1,200 6-8 1-2
    1,500 sq ft (1 story) ~1,600 8-10 2
    2,000 sq ft (2 story) ~2,200 12-15 2-3
    2,500 sq ft (2 story) ~2,800 15-18 3-4
    3,000 sq ft (2 story) ~3,400 18-22 4-5

    *Estimates assume standard window/door deductions and 2 coats

    Exterior Paint Calculator: Worked Example

    The Exterior tab of the calculator above works from the building footprint instead of wall by wall: enter the building length and width, the number of stories and the story height, the gables (number, base and height) and the garage doors, then the doors and windows as on the interior tabs. The wall material sets the coverage, from smooth wood siding (350 to 400 sq ft per gallon) and vinyl (300 to 400) down to stucco (150 to 250) and brick (100 to 150), the same ranges as the siding table above.

    For a two story house of 40 × 30 ft with 9 ft stories, two gables 30 ft wide and 8 ft high, one garage door, two doors and 14 medium windows, the calculator finds 2,760 sq ft of wall, takes off 452 sq ft of openings and paints 2,308 sq ft. In smooth wood siding with two coats and 10% waste that is 13.55 gallons, bought as two 5 gal cans, three 1 gal cans and three quarts. Primer has its own tick box, for bare or patched siding. The cost card prices the paint at economy, mid-range and premium rates, $275 to $413, $413 to $619 and $619 to $894 for this house, from the per gallon prices in the paint cost table below, and a labor rate per square foot can be added for a contractor estimate.

    Exterior paint calculator with a two story 40 by 30 ft house, two gables and a garage door: 2,308 sq ft net and 13.55 gallons of paint
    Exterior tab: 40 × 30 ft, two 9 ft stories and two gables, smooth wood siding, two coats: 13.55 gal.

    Fence and Deck Stain Calculator

    For fences, calculate the total surface area of both sides if painting the entire fence:

    Fence Sq Ft = Length × Height × 2 (for both sides)
    Example: 100′ Privacy Fence, 6′ tall
    • One side: 100 × 6 = 600 sq ft
    • Both sides: 600 × 2 = 1,200 sq ft
    • At 300 sq ft/gallon (rough wood): 1,200 ÷ 300 = 4 gallons
    • For 2 coats: 4 × 2 = 8 gallons
    Important: Exterior paint and stain have different coverage rates. Fence stain typically covers 150-300 sq ft per gallon depending on wood porosity and stain type. Always check manufacturer specifications.

    The calculator above has its own Fence and deck tab for this. Enter the fence length and height, choose one side or both, add a deck (length × width) and any railing, then pick the product. Railings are counted as a flat surface, length × height on both sides. Choosing a stain switches the primer off, since stain needs none.

    Fence and deck stain calculator with a 100 ft fence, a 16 by 12 ft deck and 40 ft of railing: 1,632 sq ft and 23.94 gallons of stain
    Fence and deck tab: rough wood stain, two coats and 10% waste for 1,632 sq ft.

    Stain and Paint Coverage in the Calculator

    Each product carries one coverage figure per coat, taken from the ranges in this guide. The label on your can is still the best guide, since brands differ.

    Product Typical range (sq ft/gal) Value used (sq ft/gal)
    Exterior paint, smooth wood 350 to 400 375
    Exterior paint, rough wood 200 to 300 250
    Stain, smooth or planed wood 150 to 300, smooth end 300
    Stain, rough or porous wood 150 to 300, porous end 150
    Example: the same 100′ fence, 6′ tall, stained on both sides, plus a 16′ × 12′ deck and 40′ of 3′ railing
    • Fence: 100 × 6 × 2 = 1,200 sq ft
    • Deck: 16 × 12 = 192 sq ft
    • Railing: 40 × 3 × 2 = 240 sq ft
    • Total: 1,632 sq ft
    • Rough or porous wood stain at 150 sq ft/gallon, 2 coats, 10% waste: 1,632 ÷ 150 × 2 × 1.1 = 23.94 gallons
    • Cans suggested by the calculator: four 5 gal and four 1 gal

    Exterior paint calculator showing house size estimates and coverage rates

    Interior & Exterior Painting Cost Calculator

    Understanding painting costs helps you budget accurately whether you’re doing it yourself or hiring professionals. Costs vary significantly based on paint quality, surface preparation, and your location, similar to how home renovation costs vary by project scope. Use this section as an interior painting estimate calculator to plan your budget.

    Paint Prices by Quality (2026 Averages)

    Paint Quality Price/Gallon Coverage Durability
    Economy (store brands) $20-30 300-350 sq ft 3-5 years
    Mid-Range (Behr Premium Plus, Valspar) $30-45 350-400 sq ft 5-8 years
    Premium (Behr Marquee, SW SuperPaint) $45-65 400-450 sq ft 8-12 years
    Ultra-Premium (BM Aura, SW Emerald) $65-100+ 400-450 sq ft 10-15+ years

    Paint Cost Comparison by Brand (2026)

    Paint prices have risen over the past few years. Here is a quick comparison of current pricing across popular brands to help your interior painting estimate calculator:

    Brand Budget Line (per gal) Mid-Range (per gal) Premium (per gal) Where to Buy
    Behr $28-35 $38-45 $48-55 Home Depot
    Sherwin-Williams $35-45 $45-55 $60-80 SW Stores
    Benjamin Moore $45-50 $55-65 $70-80+ BM Retailers
    Valspar $25-35 $35-50 $50-60 Lowe’s
    PPG/Glidden $25-30 $30-45 $45-55 Home Depot, PPG Stores

    Sherwin-Williams frequently runs 30-40% off sales, which can bring their premium lines closer to mid-range pricing. Watch for seasonal promotions at all retailers.

    DIY vs Professional Painting Costs

    DIY Interior Painting Costs

    • Paint: $30-55 per gallon (mid-range to premium)
    • Primer: $20-40 per gallon
    • Supplies: $50-150 (brushes, rollers, tape, drop cloths, trays)
    • Total for average room: $100-350
    • Total per sq ft: $0.50-1.50

    Professional Interior Painting Costs

    • Walls only: $1-3 per square foot
    • Walls + ceiling + trim: $3-6 per square foot
    • Average room: $350-900
    • Whole house (2,000 sq ft): $4,000-12,000
    • Labor accounts for: 70-85% of total cost

    Professional vs DIY painting cost comparison chart

    Professional Exterior Painting Costs

    • Per square foot: $1.50-5.00
    • 1,500 sq ft home: $2,500-5,500
    • 2,500 sq ft home: $4,000-9,000
    • Fence painting: $2-4 per square foot
    • Trim only: $1-3 per linear foot

    Painting Cost by Room

    Room DIY Cost Professional Cost
    Bathroom $75-175 $300-600
    Small Bedroom $100-225 $350-700
    Master Bedroom $150-350 $650-1,500
    Living Room $200-450 $1,000-2,200
    Kitchen $150-350 $800-1,600
    Whole House Interior $1,000-3,000 $4,000-12,000

    For more detailed guidance on planning renovation budgets, see our guide to expert architectural tips for home renovation.

    Room-by-room painting cost breakdown for DIY and professional projects

    How to Save Money on Paint Without Sacrificing Quality

    Paint can be one of the most cost-effective home improvements when you buy smart. Here are practical ways to keep your paint budget in check:

    • Wait for seasonal sales. Sherwin-Williams runs multiple 30-40% off events each year, and Behr often offers rebates at Home Depot during spring and fall.
    • Buy in 5-gallon buckets when painting multiple rooms the same color. The per-gallon price drops by roughly 10-15%.
    • Use the Lowe’s paint estimator or the Sherwin-Williams paint calculator before shopping, then compare prices online and in-store.
    • Choose a paint-and-primer-in-one product for repainting similar colors. It saves the cost of a separate primer gallon.
    • Ask for mistints. Most paint stores sell returned or mis-mixed paint at 50-75% off. These work well for closets, garages, and utility rooms.
    • Invest in quality paint for high-traffic areas (kitchen, hallways, bathrooms) and use mid-range paint for bedrooms and guest rooms where wear is lighter.

    Choosing Paint Finishes

    The right paint finish affects both appearance and durability. Consider the room’s function, lighting, and traffic when selecting finishes. This is an important aspect of interior design trends.

    Interior Paint Finishes Guide

    Finish Sheen Level Durability Best Uses
    Flat/Matte 0-10% Low Ceilings, low-traffic rooms, hides imperfections
    Eggshell 10-25% Medium Living rooms, bedrooms, dining rooms
    Satin 25-35% Medium-High Kitchens, bathrooms, hallways, family rooms
    Semi-Gloss 35-70% High Trim, doors, cabinets, high-moisture areas
    High-Gloss 70-100% Very High Accent trim, furniture, cabinets
    Rule of Thumb: Higher sheen = more durable and washable, but also shows more imperfections. Use flat or matte on walls with flaws, and semi-gloss on trim and high-traffic areas.

    Exterior Paint Finishes

    • Flat: Best for siding with imperfections; harder to clean
    • Low-Sheen/Satin: Popular choice balancing appearance and cleanability
    • Semi-Gloss: Ideal for trim, shutters, doors; very durable
    • Gloss: Maximum durability for doors and high-wear areas

    Paint finish types comparison from flat to high-gloss with recommended uses

    Surface Preparation Tips

    Proper surface preparation is crucial for paint adhesion and longevity. According to Sherwin-Williams, surface prep accounts for up to 80% of a successful paint job.

    Interior Preparation Checklist

    • Remove furniture or move to center of room and cover
    • Remove outlet covers and light switch plates
    • Fill holes and cracks with spackling compound
    • Sand patched areas smooth when dry
    • Clean walls to remove dust, grease, and cobwebs
    • Apply painter’s tape to trim, windows, and ceiling edges
    • Prime bare drywall, stains, or when making dramatic color changes
    • Lay drop cloths to protect floors

    Exterior Preparation Checklist

    • Pressure wash to remove dirt, mildew, and loose paint
    • Scrape and sand peeling or flaking paint
    • Repair or replace damaged siding, trim, or caulk
    • Prime bare wood and any repairs
    • Cover landscaping, windows, and fixtures
    • Check weather forecast. Avoid painting in extreme heat, cold, or high humidity
    • Allow surfaces to dry completely after washing (24-48 hours)
    Lead Paint Warning: Homes built before 1978 may contain lead-based paint. Disturbing lead paint can create serious health hazards. Always test for lead before scraping or sanding old paint, and follow EPA RRP guidelines if lead is present.

    Surface preparation checklist for interior and exterior painting projects

    Factors Affecting Paint Coverage

    Several variables can increase or decrease the amount of paint needed beyond basic square footage calculations:

    Surface Texture

    • Smooth drywall: Standard coverage (350-400 sq ft/gal)
    • Orange peel texture: 10-20% more paint needed
    • Knockdown texture: 20-30% more paint needed
    • Heavy texture/popcorn: 30-50% more paint needed
    • Brick/masonry: 50-100% more paint needed

    Color Changes

    • Similar colors: 2 coats typically sufficient
    • Light to dark: 2-3 coats with tinted primer
    • Dark to light: 3+ coats or primer + 2 coats
    • Covering bright colors (red, orange, yellow): Always use gray-tinted primer

    Application Method

    • Brush: Uses less paint but slower; best for detail work
    • Roller: Standard coverage; most efficient for large areas
    • Sprayer: Uses 20-40% more paint but fastest application; requires more masking

    Factors affecting paint coverage including texture, color change, and application method

    Common Paint Calculation Mistakes to Avoid

    Even with a paint calculator, these errors can throw off your estimate:

    • Forgetting to double for two coats. Most surfaces need two coats for even coverage, so always multiply your base gallon number by two.
    • Not accounting for surface texture. A knockdown or popcorn ceiling can absorb 30-50% more paint than smooth drywall.
    • Using interior coverage rates for exterior surfaces. Exterior siding (especially stucco and brick) absorbs significantly more paint per gallon.
    • Skipping primer when changing colors drastically. Going from dark to light without primer wastes paint on extra coats.
    • Spraying without adjusting your estimate. Spray application wastes 20-40% more paint than rolling, so increase your gallon count accordingly.
    • Measuring floor area instead of wall area. Your walls have a much larger surface area than your floor. Always calculate perimeter × height.

    Frequently Asked Questions

    How much paint do I need for a 12×12 room?

    For a 12′ × 12′ room with 8-foot ceilings, you’ll need approximately 1.5-2 gallons for the walls (with 2 coats) after subtracting doors and windows. If painting the ceiling too, add another gallon. This assumes standard latex paint with 350-400 sq ft/gallon coverage.

    How many square feet does a gallon of paint cover?

    A gallon of quality interior latex paint typically covers 350-400 square feet per coat on smooth surfaces. Exterior paint covers slightly less (250-350 sq ft) due to surface porosity. Primer covers approximately 200-300 sq ft per gallon. Always check the paint can for specific coverage rates.

    How much does it cost to paint the interior of a house?

    Professional interior painting costs $2-6 per square foot, or $4,000-$12,000 for an average 2,000 sq ft home. DIY costs are significantly lower at $0.50-1.50 per square foot. Costs vary based on paint quality, surface condition, ceiling height, and geographic location. Use an interior painting estimate calculator to get a number tailored to your project.

    Do I need primer before painting?

    Primer is recommended for: new drywall, bare wood, stained surfaces, when making dramatic color changes, over glossy surfaces, and on porous surfaces. Many premium paints now include primer (paint-and-primer-in-one), which works well for repainting similar colors on previously painted surfaces.

    How do I calculate paint for walls with high ceilings?

    Use the same formula: perimeter × height = wall square footage. A room with 10-foot ceilings has 25% more wall area than one with 8-foot ceilings. For vaulted or cathedral ceilings, break the wall into rectangular and triangular sections, calculate each separately, and add together.

    FAQ section illustration for paint calculator guide

    How much paint do I need for a fence?

    For a 6-foot privacy fence, calculate: length × height × 2 (for both sides) = total square feet. A 100-foot fence needs approximately 8 gallons for two coats. Wood fences are porous and absorb more paint, so use coverage rates of 200-300 sq ft/gallon.

    How much stain do I need for a deck?

    Multiply the deck length by its width, divide by the stain’s coverage per gallon and multiply by the number of coats. A 16 × 12 ft deck is 192 sq ft: at 150 sq ft per gallon for rough or porous wood, two coats take about 2.6 gallons, or about 2.8 gallons with 10% waste. Add railings separately as length × height × 2. The Fence and deck tab of the calculator works this out for the fence, the deck and the railing in one go.

    What’s the difference between interior and exterior paint?

    Exterior paint contains additives for UV resistance, mildew prevention, and flexibility for temperature changes. Interior paint focuses on washability, low VOCs, and stain resistance. Never use interior paint outside because it won’t withstand weather exposure. Exterior paint can sometimes be used indoors but may have stronger odors.

    How long does paint last once opened?

    Properly sealed latex paint lasts 2-10 years once opened. Store in a cool, dry place with the lid tightly sealed. Never freeze latex paint. Oil-based paints can last up to 15 years. Check for foul odors, lumps, or separation before using stored paint because these indicate spoilage.

    Should I buy a quart or gallon of paint?

    A quart covers approximately 100 square feet, which is enough for an accent wall, door, or small touch-up project. For anything larger, gallons are more cost-effective. Calculate your exact needs first, then round up to the nearest container size, keeping extra for touch-ups.

    How do I estimate paint for exterior trim?

    As a rule of thumb, budget 1 gallon of trim paint for every 8 gallons of body paint. For precise estimation, measure total linear feet of trim, multiply by the average width (6 inches = 0.5 feet), and divide by coverage rate (approximately 400-450 sq ft/gallon for semi-gloss). Using a trim paint calculator simplifies this process.

    How accurate is the Lowe’s paint estimator?

    The Lowe’s paint estimator provides a solid starting point, especially for standard rectangular rooms. It uses average coverage rates of 350-400 sq ft per gallon and includes man-hours estimation. For the most accurate result, measure your walls yourself and compare estimates from two or three different paint calculators. Adjust for textured walls, dramatic color changes, or porous surfaces, as online tools typically assume smooth, previously painted drywall.

    How do I use the Sherwin-Williams paint calculator?

    Visit the Sherwin-Williams paint calculator page and choose between the “Quick Calculator” (select a preset room size) or the “Custom Calculator” (enter exact wall dimensions). Input the number of doors and windows, ceiling height, and number of coats. The tool outputs the estimated gallons for your project based on Sherwin-Williams coverage specs.

    Paint calculator resources and additional tools for estimating paint needs

    Additional Resources

    Sherwin-Williams Paint CalculatorOfficial calculator with custom and quick options

    Benjamin Moore Paint CalculatorSimple calculator for walls and trim

    Behr Paint CalculatorInterior, exterior, and stain estimates

    KILZ Primer CalculatorPrimer and paint needs estimator

    Lowe’s Paint CalculatorIncludes man-hours estimation

    HomeAdvisor Paint CalculatorDIY and professional cost estimates

    EPA Lead Paint InformationSafety guidelines for older homes

    PPG Paint CalculatorProfessional-grade paint estimates

    Glidden Paint CalculatorQuick room-size presets with gallon estimates

    This Old House: How Much Paint Do I Need?Step-by-step calculation guide with examples

    Tools on Illustrarch

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