How to calculate concrete
- Work out the volume. Length × width × thickness, all in feet, gives cubic feet.
- Multiply by 150. Normal concrete weighs about 150 lb per cubic foot, 4,050 lb per cubic yard.
- Convert to tons. Divide pounds by 2,000 for US tons.
- Check the load. Compare with what your trailer, truck or floor is rated for.
Worked example: a 12 × 20 ft patio, 4 inches thick
- Volume: 12 × 20 × (4 ÷ 12) = 80.0 cu ft (2.96 cubic yards).
- Weight: 80.0 × 150 = 12,000 lb, or 6.0 tons.
- The calculator adds your waste percentage to the volume, so its weight is a little higher.
Concrete weight by volume
| Cubic yards | Cubic feet | Pounds | Tons |
|---|---|---|---|
| 0.25 | 6.8 | 1,013 | 0.5 |
| 0.50 | 13.5 | 2,025 | 1.0 |
| 1.00 | 27.0 | 4,050 | 2.0 |
| 2.00 | 54.0 | 8,100 | 4.0 |
| 3.00 | 81.0 | 12,150 | 6.1 |
| 5.00 | 135.0 | 20,250 | 10.1 |
| 10.00 | 270.0 | 40,500 | 20.3 |
Normal concrete at 150 lb per cubic foot. US tons of 2,000 lb.
Weight of a concrete slab
| Thickness | lb per sq ft | 10 × 10 ft slab (lb) | 12 × 24 ft slab (lb) |
|---|---|---|---|
| 3 in | 37.5 | 3,750 | 10,800 |
| 4 in | 50.0 | 5,000 | 14,400 |
| 5 in | 62.5 | 6,250 | 18,000 |
| 6 in | 75.0 | 7,500 | 21,600 |
| 8 in | 100.0 | 10,000 | 28,800 |
Normal concrete at 150 lb per cubic foot.
Concrete formulas by shape
All measurements in feet; divide inches by 12 first. Results are in cubic feet.
- Slab
- length × width × thickness
- Round slab
- π × (diameter ÷ 2)² × thickness
- Continuous footing
- total length × width × depth
- Pad footing
- length × width × depth × number of footings
- Monolithic slab
- length × width × thickness + perimeter band × (edge depth − thickness), where perimeter band = length × width − (length − 2 × edge width) × (width − 2 × edge width)
- Bell footing
- π × r² × pier height + π × bell height ÷ 3 × (R² + R × r + r²), with r = pier radius and R = bell radius
- Wall
- length × height × thickness
- Column / pier
- π × (diameter ÷ 2)² × height
- Post hole
- (hole area − post area) × depth; round hole π × (diameter ÷ 2)², square hole width²
- Tube / ring
- π × [(outer ÷ 2)² − (inner ÷ 2)²] × height
- Curb & gutter
- [curb depth × (curb height + flag thickness) + gutter width × flag thickness] × length
- Steps (solid, n steps)
- width × rise × run × (1 + 2 + … + n). With a landing, the landing is the top step: width × rise × [run × (1 + … + (n − 1)) + landing depth × n]
Cubic yards = cubic feet ÷ 27.
Frequently asked questions
How much does a cubic yard of concrete weigh?
About 4,050 lb, a little over 2 tons, at 150 lb per cubic foot.
How much does a 4 inch concrete slab weigh per square foot?
About 50 lb per square foot; 75 lb at 6 inches.
How much does a 10x10 concrete slab weigh?
At 4 inches thick it is 33.3 cubic feet, about 5,000 lb or 2.5 tons.
Does reinforced concrete weigh more?
A little: steel adds a few pounds per cubic foot, so reinforced concrete is often taken as about 150–155 lb per cubic foot. Lightweight concrete is much lighter, around 90–115 lb.
About the prices
Costs are estimated ranges with source and date, never a quote. Enter your local prices under "Use your own prices", or read how we estimate prices.