Cubic yards from dimensions — with waste factor
How to Calculate Concrete Yardage
Answer first: Cubic yards = (Length × Width × Thickness in feet) ÷ 27. Add 10% waste. Use the calculator below for instant results.
Formula
yd³ = (L × W × T) ÷ 27
L, W in feet. T in feet (divide inches by 12). Add 5–15% waste.
10 × 10 ft, 4 in thick
1.23 yd³ with 10% waste
That's about 56 bags of 80 lb concrete.
Calculate Concrete Yardage
10 × 10 × (4/12) ÷ 27 × 1.10 = 1.36 yd³
Cubic yards
1.36
Cubic feet
36.7
80 lb bags
62
Interactive workflow
Run the numbers, then save or export the project
The concrete yardage formula — explained
Three steps to go from dimensions to a ready-mix order.
| Benchmark says | Replace with local input | Next check |
|---|---|---|
| Step 1: cubic feet | Multiply length (ft) × width (ft) × thickness (ft). Convert thickness from inches: 4 in = 4/12 = 0.333 ft. | 10 ft × 10 ft × 0.333 ft = 33.3 cubic feet. |
| Step 2: cubic yards | Divide cubic feet by 27 (there are 27 cubic feet in a cubic yard). | 33.3 ÷ 27 = 1.23 cubic yards. |
| Step 3: add waste | Multiply by 1.10 (10% waste) for a typical pour. | 1.23 × 1.10 = 1.35 yd³ to order. The calculator above does all three steps. |
Concrete yardage checklist
Before calling a ready-mix plant with your order.
| Signal to check | What it means | Next step |
|---|---|---|
| Dimensions measured | Length, width, and thickness measured at the actual site. | Measure twice — being off by 1 inch on a large slab adds up fast. |
| Waste added | Added 5–15% waste to the calculated volume. | Use 10% for flat slabs. Add more for steps, curved edges, or uneven sub-base. |
| Order rounded up | Rounded up to the nearest 0.25 yd³. | Plants typically sell in 0.25 yd³ increments. Running short mid-pour causes cold joints. |
| Minimum checked | Confirmed the plant's minimum load (typically 1–3 yd³). | Small orders may trigger a short-load fee. Ask when you call. |
Related concrete planning tools
Move from a single calculation into a purchase, proposal, or pour-day decision with connected calculators and checklists.
How do I calculate concrete yardage?
Multiply length × width × (thickness ÷ 12) to get cubic feet, then divide by 27. Formula: yd³ = (L × W × T) ÷ 27, where T is thickness in feet (inches ÷ 12). Add 10% waste.
How many cubic yards of concrete do I need for a 10×10 slab?
A 10×10 ft slab at 4 inches thick needs 1.23 cubic yards (with 10% waste). The calculation: 10 × 10 × (4/12) = 33.3 ft³ ÷ 27 = 1.23 yd³ × 1.10 waste = 1.35 yd³ to order.
How many 80 lb bags of concrete in a cubic yard?
About 45 bags of 80 lb concrete (at 0.6 ft³ each) make one cubic yard. With 10% waste, plan for about 50 bags per yard.
How much is a yard of concrete?
Ready-mix concrete typically costs $150–$200 per cubic yard plus a delivery fee of $100–$200. Prices vary by region and mix design. Use the concrete cost calculator for a local estimate.
Do I need to add waste when calculating concrete?
Yes. Always add 5–15% to your calculated volume. Use 10% for flat, simple slabs. Use 15% for uneven ground, complex shapes, or forms you're not sure about. Running short mid-pour causes cold joints that weaken the slab.
Planning disclaimer
Calculated volumes include a standard waste factor. Actual concrete needed depends on sub-base conditions, form accuracy, and pour technique. Confirm your order with a ready-mix supplier.