How to calculate concrete
- Work out the volume. Length × width × thickness in metres gives cubic metres.
- Multiply by 2,400. Normal concrete weighs about 2,400 kg per cubic metre.
- Convert to tonnes. Divide kilograms by 1,000: 1 m³ is about 2.4 tonnes.
- Check the load. Compare with what your trailer, ute or floor is rated for.
Worked example: a 6 × 6 m garage slab, 100 mm thick
- Volume: 6 × 6 × 0.1 = 3.60 m³.
- Weight: 3.60 m³ × 2,402.8 kg = 8,650 kg, about 8.6 tonnes.
- The calculator adds your waste percentage to the volume, so its weight is a little higher.
Concrete weight by volume
| Cubic metres | Kilograms | Tonnes |
|---|---|---|
| 0.10 | 240 | 0.24 |
| 0.25 | 601 | 0.60 |
| 0.50 | 1,201 | 1.20 |
| 1.00 | 2,403 | 2.40 |
| 2.00 | 4,806 | 4.81 |
| 3.00 | 7,208 | 7.21 |
| 5.00 | 12,014 | 12.01 |
Normal concrete at 2,403 kg per m³.
Weight of a concrete slab
| Thickness | kg per m² | 6 × 3 m slab (kg) | 6 × 6 m slab (kg) |
|---|---|---|---|
| 75 mm | 180 | 3,244 | 6,487 |
| 100 mm | 240 | 4,325 | 8,650 |
| 125 mm | 300 | 5,406 | 10,812 |
| 150 mm | 360 | 6,487 | 12,975 |
| 200 mm | 481 | 8,650 | 17,300 |
Normal concrete at 2,403 kg per m³.
Concrete formulas by shape
All measurements in metres; divide millimetres by 1,000 first. Results are in cubic metres.
- 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]
1 m³ = 1,000 litres.
Frequently asked questions
How much does 1 m³ of concrete weigh?
About 2,400 kg, or 2.4 tonnes. We use 2,403 kg (150 lb per cubic foot), the same figure as the calculator.
How much does a 100 mm slab weigh per square metre?
About 240 kg per m²; 360 kg at 150 mm.
How much does a 6 × 3 m slab weigh?
At 100 mm thick it is 1.8 m³, about 4,325 kg or 4.3 tonnes.
Does reinforced concrete weigh more?
A little: with reo it is often taken as about 2,500 kg per m³. Lightweight concrete is much lighter, roughly 1,400 to 1,850 kg.
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.