Concrete Calculator
Estimate concrete volume for slabs and footings.
Concrete Calculator
Everything you need to know
About the Concrete Calculator
Pouring concrete is one of the most common DIY and professional construction tasks, but ordering the wrong amount is expensive and frustrating. Order too little, and your project stops while you wait for another delivery. Order too much, and you pay for concrete that hardens in the truck. Our concrete calculator eliminates the guesswork by giving you precise volume measurements for slabs, footings, columns, curbs, and more.
Whether you are building a backyard patio, pouring a driveway, setting fence posts, or laying a foundation, knowing the exact amount of concrete needed ensures your project stays on budget and on schedule.
Why Accurate Concrete Calculation Matters
Cost Control
Concrete is sold by the cubic yard, with prices ranging from $120 to $200 per cubic yard depending on your location, mix type, and delivery distance. A miscalculation of just one cubic yard can cost $150 or more.
Project Continuity
A concrete truck holds 8-10 cubic yards. If you run short, you may face a minimum load charge of $100-150 for a partial delivery, plus hours of downtime.
Waste Reduction
Excess concrete must be disposed of properly, which can incur dump fees. Accurate ordering is better for your wallet and the environment.
How to Calculate Concrete Volume
Formula
Volume = Length × Width × Depth
All measurements must be in the same unit before multiplying. The result is then converted to cubic yards for ordering.
Conversion: 1 cubic yard = 27 cubic feet = 46,656 cubic inches
Slab Calculation Example
Project: Backyard patio measuring 12 feet long, 10 feet wide, 4 inches thick
- Convert depth to feet: 4 inches = 0.333 feet
- Volume in cubic feet: 12 × 10 × 0.333 = 40 cubic feet
- Volume in cubic yards: 40 ÷ 27 = 1.48 cubic yards
- With 10% waste factor: 1.48 × 1.10 = 1.63 cubic yards → round up to 1.75 yards
Footing Calculation Example
Project: Foundation footing 40 feet long, 18 inches wide, 12 inches deep
- Convert width and depth to feet: 18 inches = 1.5 feet; 12 inches = 1 foot
- Volume in cubic feet: 40 × 1.5 × 1 = 60 cubic feet
- Volume in cubic yards: 60 ÷ 27 = 2.22 cubic yards
- With 10% waste: 2.22 × 1.10 = 2.44 → round up to 2.5 yards
Round Column Example
Project: Cylindrical column 3 feet in diameter, 10 feet tall
- Radius = 1.5 feet
- Volume = π × r² × height = 3.14159 × (1.5)² × 10 = 3.14159 × 2.25 × 10 = 70.69 cubic feet
- Volume in cubic yards: 70.69 ÷ 27 = 2.62 cubic yards
Standard Concrete Thickness by Project
| Project Type | Recommended Thickness | Notes |
|---|---|---|
| Sidewalk / walkway | 4 inches | With control joints every 4-5 feet |
| Patio (foot traffic only) | 4 inches | Reinforced with wire mesh or rebar |
| Driveway (passenger cars) | 4-5 inches | 4,000 PSI minimum, reinforced |
| Driveway (trucks / RVs) | 5-6 inches | 4,000+ PSI, heavy rebar |
| Garage floor | 4-6 inches | Depends on vehicle weight |
| Foundation slab | 4-6 inches | Vapor barrier underneath |
| Footings | 12-24 inches | Below frost line, per building code |
| Steps | 6-8 inches | Treads 12 inches, risers 7 inches |
| Fence posts | 6-12 inches diameter × 24-36 inches deep | Post hole concrete |
Bagged Concrete vs. Ready-Mix Truck
Bagged Concrete (DIY Projects)
Each 80-pound bag yields approximately 0.6 cubic feet of concrete.
| Project Volume | 80 lb Bags Needed | 60 lb Bags Needed |
|---|---|---|
| 1 cubic foot | 2 bags | 3 bags |
| 10 cubic feet | 17 bags | 23 bags |
| 27 cubic feet (1 cubic yard) | 45 bags | 60 bags |
Best for: Projects under 1 cubic yard, remote locations, small repairs
Cost: $4-6 per 80-pound bag = $180-270 per cubic yard (more expensive than ready-mix for large jobs)
Ready-Mix Truck (Large Projects)
| Truck Size | Capacity | Best For |
|---|---|---|
| Mini truck | 3-4 cubic yards | Tight access areas |
| Standard truck | 8-10 cubic yards | Most residential jobs |
| Tandem truck | 10-12 cubic yards | Large commercial jobs |
Best for: Projects over 1 cubic yard, foundations, driveways, patios
Cost: $120-200 per cubic yard + $50-150 delivery fee
Cost Estimation Guide
Material Costs (Per Cubic Yard)
| Component | Cost Range |
|---|---|
| Standard concrete (3,000 PSI) | $120-150 |
| High-strength concrete (4,000 PSI) | $140-170 |
| High-early concrete | $160-200 |
| Colored concrete | $150-200 |
| Exposed aggregate | $160-220 |
| Reinforcement (rebar/mesh) | $15-30 per cubic yard |
Labor Costs (If Hiring)
| Task | Cost Range |
|---|---|
| Concrete delivery | $50-150 per load |
| Finishing labor | $3-8 per square foot |
| Formwork setup | $2-5 per square foot |
| Reinforcement installation | $1-3 per square foot |
Reinforcement Options
| Type | Use Case | Cost |
|---|---|---|
| Wire mesh (6×6, W1.4/W1.4) | Light-duty slabs | $0.35-0.50 per sq ft |
| Rebar (#4, 1/2 inch) | Medium-duty, footings | $0.65-0.90 per linear foot |
| Rebar (#5, 5/8 inch) | Heavy-duty, foundations | $1.00-1.40 per linear foot |
| Fiber mesh (added to mix) | Crack resistance | $8-12 per cubic yard |
Step-by-Step Pouring Guide
- Excavate and grade: Remove topsoil and organic material. Compact the subgrade.
- Install forms: Use 2×4 or 2×6 lumber secured with stakes. Ensure level and square.
- Add base: Lay 4-6 inches of compacted gravel for drainage.
- Install reinforcement: Place wire mesh or rebar on chairs so it sits in the middle of the slab.
- Pour concrete: Start at the far end and work backward. Pour evenly to avoid weak spots.
- Screed: Use a straight 2×4 to level the concrete across the forms.
- Float: Use a magnesium float to smooth the surface and embed aggregate.
- Edge and joint: Use an edging tool on the perimeter and a groover for control joints.
- Trowel: For a smooth finish, use a steel trowel when the concrete is firm.
- Cure: Keep concrete moist for 3-7 days. Cover with plastic or apply curing compound.
Frequently Asked Questions
How much concrete do I need for a 10×10 patio?
At 4 inches thick: 10 × 10 × 0.333 = 33.3 cubic feet = 1.23 cubic yards. With 10% waste: 1.4 cubic yards.
How many 80-pound bags make a yard?
Approximately 45 bags of 80-pound concrete mix make one cubic yard.
Should I order extra concrete?
Yes. Add 5-10% to your calculation to account for spillage, over-excavation, and measurement errors.
How long does concrete take to cure?
Concrete reaches initial set in 4-6 hours, can bear light foot traffic in 24-48 hours, reaches 70% strength in 7 days, and full strength in 28 days.
What happens if it rains on fresh concrete?
Light rain is usually fine if the surface has set (4+ hours). Cover fresh concrete with plastic if heavy rain is expected within the first 24 hours.