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Concrete & Material Calculator: Estimate Bags, Yards, Blocks & Cost
Whether you’re pouring a driveway, setting fence posts, or building a foundation, calculating the right amount of concrete is essential to avoid costly shortages or waste. Our free concrete calculator helps you estimate volume in cubic yards, determine how many bags you need, and calculate material costs for any project.
Understanding concrete calculations is fundamental to construction—similar to how bubble diagrams help architects plan spatial relationships, accurate material estimates ensure your project succeeds. This comprehensive guide covers formulas for slabs, footings, columns, sonotubes, and concrete block walls with real-world examples and cost data.
Basic Concrete Calculation Formula
The foundation of all concrete calculations is the simple volume formula. Once you know the volume, you can convert to cubic yards and determine bag quantities or ready-mix needs.
Volume (cu ft) = Length (ft) × Width (ft) × Thickness (ft)📐 Essential Conversions
- Cubic Feet to Cubic Yards: Divide by 27 (1 cubic yard = 27 cubic feet)
- Inches to Feet: Divide by 12
- Cubic Yards to Cubic Meters: Multiply by 0.7646
- 1 Cubic Yard = 27 cubic feet = 46,656 cubic inches = 0.76 cubic meters
Measure Dimensions
Measure the length, width, and thickness/depth of your project area in feet. Convert any inch measurements to feet by dividing by 12.
Calculate Cubic Feet
Multiply Length × Width × Thickness to get volume in cubic feet. For irregular shapes, break into rectangles and add them together.
Convert to Cubic Yards
Divide the cubic feet by 27 to get cubic yards. This is the standard measurement for ordering ready-mix concrete.
Add Waste Factor
Add 5-10% extra for waste, spillage, and uneven subgrade. For complex shapes or inexperienced DIYers, add 10-15%.
Example: 10×10 Slab, 4 Inches Thick
• Convert thickness: 4 inches ÷ 12 = 0.333 feet
• Volume: 10 × 10 × 0.333 = 33.3 cubic feet
• Cubic yards: 33.3 ÷ 27 = 1.23 cubic yards
• With 10% waste: 1.23 × 1.10 = 1.35 cubic yards
Concrete Bag Calculator
For smaller projects where ordering a concrete truck isn’t practical, pre-mixed bags are the solution. Understanding bag yields helps you buy the right quantity without making multiple trips to the store.
Concrete Bag Yields
| Bag Size | Yield (cu ft) | Yield (cu yd) | Bags per Cubic Yard | Typical Price |
|---|---|---|---|---|
| 40 lb (Quikrete/Sakrete) | 0.30 | 0.011 | 90 | $3.50 – $5.00 |
| 50 lb | 0.375 | 0.014 | 72 | $4.00 – $5.50 |
| 60 lb (Quikrete/Sakrete) | 0.45 | 0.017 | 60 | $4.50 – $6.50 |
| 80 lb (Quikrete/Sakrete) | 0.60 | 0.022 | 45 | $5.50 – $8.00 |
Number of Bags = Total Cubic Feet ÷ Bag Yield (cu ft)Example: 10×10 Slab Using 80 lb Bags
• Volume needed: 33.3 cubic feet (from earlier calculation)
• Bags: 33.3 ÷ 0.60 = 55.5 bags
• With 10% extra: 61 bags of 80 lb concrete
Concrete Slab Calculator
Concrete slabs are the most common residential project, used for patios, driveways, garage floors, and foundations. The thickness varies by application, affecting both material needs and cost.
Recommended Slab Thickness by Application
| Application | Minimum Thickness | Recommended | Notes |
|---|---|---|---|
| Walkway/Sidewalk | 3″ | 4″ | Light foot traffic only |
| Patio | 4″ | 4″ | Standard residential use |
| Driveway (cars) | 4″ | 4-5″ | Use 5″ for heavy vehicles |
| Driveway (trucks/RVs) | 5″ | 6″ | Requires reinforcement |
| Garage Floor | 4″ | 4-6″ | 6″ for workshops |
| Shed Foundation | 4″ | 4″ | Gravel base recommended |
| House Foundation | 6″ | 6-8″ | Requires engineering |
Concrete Coverage by Thickness
| Thickness | Sq Ft per Cubic Yard | 80 lb Bags per 10 Sq Ft |
|---|---|---|
| 2 inches | 162 sq ft | 1.1 bags |
| 3 inches | 108 sq ft | 1.7 bags |
| 4 inches | 81 sq ft | 2.2 bags |
| 5 inches | 65 sq ft | 2.8 bags |
| 6 inches | 54 sq ft | 3.3 bags |
| 8 inches | 40.5 sq ft | 4.4 bags |
Common Slab Sizes
| Slab Size | 4″ Thick (cu yd) | 6″ Thick (cu yd) | 80 lb Bags (4″) |
|---|---|---|---|
| 8×8 ft (64 sq ft) | 0.79 | 1.19 | 36 |
| 10×10 ft (100 sq ft) | 1.23 | 1.85 | 56 |
| 12×12 ft (144 sq ft) | 1.78 | 2.67 | 80 |
| 10×20 ft (200 sq ft) | 2.47 | 3.70 | 111 |
| 20×20 ft (400 sq ft) | 4.94 | 7.41 | 222 |
| 20×24 ft (480 sq ft) | 5.93 | 8.89 | 267 |
Concrete Footing Calculator
Footings distribute the load from walls and columns to the soil below, preventing settling and structural damage. Proper footing design is critical for resilient construction that withstands environmental stresses.
Footing Size Guidelines
| Wall Thickness | Footing Width | Footing Depth | Rule |
|---|---|---|---|
| 6 inches | 12 inches | 6 inches | Width = 2× wall |
| 8 inches | 16 inches | 8 inches | Depth = wall thickness |
| 10 inches | 20 inches | 10 inches | Standard residential |
| 12 inches | 24 inches | 12 inches | Heavy-duty |
Cubic Yards = (Length ft × Width in × Depth in) ÷ 324Example: Foundation Footing (30 ft long, 16″ wide, 8″ deep)
• Formula: (30 × 16 × 8) ÷ 324 = 3,840 ÷ 324
• Result: 11.85 cubic feet = 0.44 cubic yards
• For 120 linear feet (house perimeter): 1.76 cubic yards
Frost Depth Requirements
Footings must extend below the frost line to prevent heaving. Depth requirements vary by region:
| Region | Typical Frost Depth | Examples |
|---|---|---|
| Southern US | 0-12 inches | Florida, Texas, Arizona |
| Central US | 24-36 inches | Kansas, Missouri, Kentucky |
| Northern US | 36-48 inches | Minnesota, Wisconsin, Maine |
| Alaska/Mountain | 48-72+ inches | Alaska, mountain regions |
Sonotube & Column Calculator
Sonotubes (cylindrical concrete forms) are used for deck posts, light poles, fence supports, and round columns. The calculation uses the cylinder volume formula.
Volume (cu ft) = π × (Diameter/24)² × Height (ft)Sonotube Concrete Requirements
| Diameter | Per Foot Height (cu ft) | 80 lb Bags per Foot | 4 ft Column (cu ft) |
|---|---|---|---|
| 6 inches | 0.20 | 0.33 | 0.79 |
| 8 inches | 0.35 | 0.58 | 1.40 |
| 10 inches | 0.55 | 0.91 | 2.18 |
| 12 inches | 0.79 | 1.31 | 3.14 |
| 14 inches | 1.07 | 1.78 | 4.28 |
| 16 inches | 1.40 | 2.33 | 5.58 |
| 18 inches | 1.77 | 2.95 | 7.07 |
| 24 inches | 3.14 | 5.24 | 12.57 |
Example: 6 Deck Posts (12″ diameter × 4 ft deep)
• Volume per post: π × (12/24)² × 4 = 3.14 × 0.25 × 4 = 3.14 cu ft
• Total for 6 posts: 3.14 × 6 = 18.84 cu ft = 0.70 cu yd
• 80 lb bags: 18.84 ÷ 0.60 = 32 bags
Concrete Block Calculator
Concrete masonry units (CMU) or cinder blocks are essential for walls, foundations, and retaining structures. Understanding block quantities, mortar needs, and fill requirements is important for construction projects involving essential building materials.
Standard CMU Block Sizes
| Nominal Size | Actual Size | Face Area (sq ft) | Blocks per 100 sq ft |
|---|---|---|---|
| 4×8×16″ | 3⅝×7⅝×15⅝” | 0.89 | 113 |
| 6×8×16″ | 5⅝×7⅝×15⅝” | 0.89 | 113 |
| 8×8×16″ (standard) | 7⅝×7⅝×15⅝” | 0.89 | 113 |
| 10×8×16″ | 9⅝×7⅝×15⅝” | 0.89 | 113 |
| 12×8×16″ | 11⅝×7⅝×15⅝” | 0.89 | 113 |
Blocks Needed = (Wall Length × Wall Height) ÷ 0.89 sq ftMortar & Fill Requirements
| Material | Amount per 100 Blocks | Notes |
|---|---|---|
| Mortar Mix (80 lb bags) | 8-9 bags | For standard 3/8″ joints |
| Sand (for mortar) | 1,000 lbs / 0.5 cu yd | If mixing from scratch |
| Grout/Fill (8″ blocks) | 0.8 cu yd | For fully grouted cores |
| Rebar (vertical) | Every 4 ft (16-24″ o.c.) | Check local codes |
Example: Block Wall (20 ft long × 8 ft high)
• Wall area: 20 × 8 = 160 sq ft
• Blocks: 160 ÷ 0.89 = 180 blocks
• With 5% waste: 189 blocks
• Mortar: 189 ÷ 100 × 8.5 = 16 bags (80 lb)
• Fill (if grouting): 189 × 0.008 cu yd = 1.5 cu yd
Concrete Cost Calculator
Understanding concrete costs helps you budget accurately and choose between DIY mixing and ready-mix delivery. Prices vary by region and material choice—just as choosing the right building materials impacts overall project costs.
Ready-Mix Concrete Prices (2024-2025)
| Concrete Type | Price per Cubic Yard | PSI Rating | Best Use |
|---|---|---|---|
| Standard Mix | $150 – $180 | 2,500 PSI | Patios, sidewalks |
| Residential Mix | $160 – $195 | 3,000 PSI | Driveways, slabs |
| High-Strength | $175 – $220 | 4,000 PSI | Foundations, heavy loads |
| High-Performance | $200 – $255 | 6,000+ PSI | Commercial, structural |
| Fiber-Reinforced | $185 – $230 | 3,000+ PSI | Crack-resistant applications |
Additional Ready-Mix Costs
- Delivery Fee: $0 – $75 (typically free within 10-20 mile radius)
- Short-Load Fee: $40 – $55 per cubic yard for orders under 10 yards
- Saturday Delivery: +$100 – $200
- Waiting Time: $2 – $4 per minute after 5-7 minutes
- Pump Truck: $150 – $300+ for hard-to-reach locations
DIY vs. Ready-Mix Cost Comparison
| Factor | DIY (Bags) | Ready-Mix |
|---|---|---|
| Material Cost per Cu Yd | $250 – $360 (45 bags × $5.50-8) | $150 – $195 |
| Labor Time | 4-8 hours per yard | Pour in 30-60 minutes |
| Equipment Needed | Mixer or mixing tub | None (truck pours) |
| Best For | Under 1 cubic yard | 1+ cubic yards |
| Consistency | Variable | Factory controlled |
💰 Cost Examples by Project
- 10×10 Patio (4″): DIY: $340 (61 bags) | Ready-Mix: $220-270 + delivery
- 20×20 Driveway (4″): DIY: $1,220 (222 bags) | Ready-Mix: $990-1,220 (~5 yards)
- 8 Deck Posts (12″ × 4′): DIY: $235 (42 bags)
- 30 ft Footing (16″ × 8″): DIY: $110 (20 bags) | Ready-Mix: $100-130
Installed Concrete Costs
For professional installation, expect to pay $6-$12 per square foot, including materials, labor, and finishing:
| Project Type | Cost per Sq Ft | Typical Total |
|---|---|---|
| Basic Slab/Patio | $4 – $8 | $400 – $2,400 |
| Driveway | $6 – $15 | $2,400 – $8,600 |
| Garage Floor | $6 – $12 | $2,400 – $7,000 |
| Foundation Slab | $6 – $14 | $12,000 – $28,000 |
| Stamped/Decorative | $12 – $25 | $3,600 – $15,000 |
Project-Specific Calculators
🏠 Driveway Calculator
Standard size: 12′ × 20′ × 4″
Volume: 2.96 cubic yards
80 lb bags: 133 bags
Cost (ready-mix): $475 – $575
🪑 Patio Calculator
Standard size: 12′ × 12′ × 4″
Volume: 1.78 cubic yards
80 lb bags: 80 bags
Cost (ready-mix): $285 – $350
🏗️ Foundation Footing
Standard: 16″ wide × 8″ deep
Per 10 linear ft: 0.15 cu yd
120 ft perimeter: 1.76 cu yd
Cost: $280 – $340
📍 Fence Post Holes
Standard: 8″ diameter × 3′ deep
Per post: 1.05 cu ft
80 lb bags per post: 1.75
10 posts: 18 bags
Tips for Accurate Concrete Calculations
- Always add extra: Order 5-10% more than calculated to account for waste, spillage, and uneven subgrade
- Add 1/4″ to thickness: This accounts for minor subgrade variations and ensures coverage
- Break complex shapes into rectangles: Calculate each section separately and add together
- For sloped slabs: Use average thickness: (min thickness + max thickness) ÷ 2
- Round up ready-mix orders: Most suppliers don’t sell partial yards; better to have extra than run short
- Consider weather: Hot weather requires faster placement; cold weather needs additives
- Plan for curing: Concrete reaches 70% strength in 7 days, full strength in 28 days
Frequently Asked Questions
How do I calculate yards of concrete?
Calculate cubic yards by multiplying Length × Width × Thickness (all in feet), then dividing by 27. For example, a 10×10 slab at 4 inches thick: 10 × 10 × 0.333 = 33.3 cubic feet ÷ 27 = 1.23 cubic yards. Always add 5-10% extra for waste.
How many bags of concrete do I need for a 10×10 slab?
For a 10×10 slab at 4 inches thick, you need approximately 56 bags of 80 lb concrete or 84 bags of 60 lb concrete. With 10% extra for waste, order 61 bags (80 lb). The slab requires 1.23 cubic yards of concrete.
How much does a cubic yard of concrete cost?
Ready-mix concrete costs $150 to $195 per cubic yard for standard residential mixes (3,000 PSI). The national average is approximately $180 per cubic yard. Additional fees may apply for short loads (under 10 yards), Saturday delivery, or pump trucks. A cubic yard weighs approximately 4,000 lbs.
How many 80 lb bags of concrete make 1 cubic yard?
It takes approximately 45 bags of 80 lb concrete to make 1 cubic yard. Each 80 lb bag yields about 0.60 cubic feet or 0.022 cubic yards of concrete. For 60 lb bags, you need 60 bags per yard; for 40 lb bags, you need 90 bags per yard.
How do I calculate concrete for a sonotube?
Use the cylinder formula: Volume = π × (Diameter/24)² × Height. For a 12-inch diameter tube that’s 4 feet deep: 3.14 × (0.5)² × 4 = 3.14 cubic feet. Divide by 0.60 to get 80 lb bags needed: approximately 5-6 bags per 12″ × 4′ sonotube.
How many concrete blocks do I need for a wall?
Divide the wall area by 0.89 sq ft (the face area of a standard 8×8×16 block including mortar joint). For a 20×8 foot wall: 160 sq ft ÷ 0.89 = 180 blocks. Add 5-10% for cuts and waste. You’ll also need about 8-9 bags of mortar mix per 100 blocks.
What thickness should a concrete driveway be?
Standard residential driveways should be 4 inches thick for regular car traffic. For heavy vehicles like trucks or RVs, use 5-6 inches. Commercial driveways may require 6-8 inches with reinforcement. Always use a compacted gravel base and consider wire mesh or fiber reinforcement.
Should I use bags or ready-mix concrete?
Use bags for projects under 1 cubic yard (small repairs, fence posts, small slabs). Order ready-mix for 1+ cubic yards—it’s more economical, saves significant labor (4-8 hours per yard vs. 30-60 minutes), and provides consistent quality. The break-even point is typically around 30-40 bags.
How deep should concrete footings be?
Footings must extend at least 12 inches below the frost line, which varies by region (12-72 inches depending on climate). Standard footing depth equals the wall thickness being supported. Check local building codes for specific requirements. Foundation footings typically need to rest on undisturbed soil.
How much waste factor should I add?
Add 5-10% for standard projects with level subgrade and simple shapes. Add 10-15% for irregular shapes, sloped sites, or inexperienced DIYers. For professional pours with proper preparation, 5% is usually sufficient. Some contractors add 1/4″ to the planned slab thickness instead of a percentage.
Additional Resources
Concrete Network CalculatorComprehensive calculator with cost estimates
Calculator.net Concrete ToolMultiple shape options and formulas
CalculatorSoupSlabs, footings, walls, columns, steps
Inch CalculatorYards and bag estimates with formulas
CEMEX CalculatorReady-mix concrete volume estimator
Omni Sonotube CalculatorDetailed column/tube calculations
CMU Block CalculatorBlock, mortar, and grout estimates
HomeGuide Slab Costs2026 concrete pricing data
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