Concrete is measured and ordered in cubic yards. The formula for a rectangular pour is:
Volume (cu yd) = Length (ft) × Width (ft) × Depth (ft) ÷ 27
Divide by 27 because there are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft = 27).
| Project | Dimensions | Thickness | Cubic Yards |
|---|---|---|---|
| Small patio | 10 × 10 ft | 4 in | 1.2 yd³ |
| Standard driveway | 10 × 20 ft | 4 in | 2.5 yd³ |
| Two-car driveway | 20 × 40 ft | 4 in | 10 yd³ |
| Garage floor | 20 × 20 ft | 4 in | 5 yd³ |
| Sidewalk (50 ft) | 50 × 4 ft | 4 in | 2.5 yd³ |
| House foundation (perimeter) | varies | 8 in | Calculate per section |
If you're doing a small project with bags instead of ready-mix delivery:
For a 10×10 patio at 4" thick (1.2 cubic yards): 1.2 × 45 = 54 bags of 80-lb concrete (plus 10% waste = 60 bags).
For a strip footing or column footing, calculate the volume the same way — length × width × height. For a round column footing, use: π × radius² × depth.
Example: Round footing 18" diameter, 24" deep: 3.14159 × (0.75)² × 2 = 3.53 cubic feet = 0.13 cubic yards.
Ready-mix concrete is typically ordered in 0.5 cubic yard increments. Minimum orders are usually 1 yard. Most trucks deliver up to 10 yards per load.
Use our Concrete Calculator to get an exact estimate for your project, or our Footing Calculator for foundation work.
Length (ft) × Width (ft) × Depth (ft) ÷ 27. For a 10×10 ft slab at 4 inches thick: 10 × 10 × 0.333 ÷ 27 = 1.23 cubic yards.
A 10×10 ft slab at 4 inches thick requires 1.23 cubic yards of concrete. With 10% waste, order 1.35 cubic yards. At 6 inches thick, you need 1.85 cubic yards.
45 bags of 80-lb premixed concrete equals one cubic yard. 60-lb bags require 60 bags per cubic yard.
Yes. Always order 10% more than your calculated volume to account for waste, spillage, slight variations in form depth, and the fact that you can't return partial loads.
Residential driveways are typically 4 inches thick for passenger cars. For vehicles over 5,000 lbs or heavy truck traffic, 6 inches is recommended.