How to Calculate Concrete
What is Concrete?
Concrete is made of cement, sand, gravel, and water. Calculating the volume before ordering or mixing prevents expensive over-ordering or frustrating shortages. Volume is always measured in cubic feet or cubic yards.
Step-by-Step Guide
- 1Measure length, width, and depth of the pour in feet
- 2Volume (cubic feet) = length × width × depth
- 3Cubic yards = cubic feet ÷ 27
- 4Add 5–10% waste factor for form overruns and spillage
Worked Examples
Input
20×15 ft slab, 4 in (0.33 ft) deep
Result
3.33 yd³ + 10% = 3.67 yd³
20×15×0.33=99 ft³÷27=3.67
Input
Footing: 40×1×2 ft
Result
2.96 yd³
80 ft³÷27