Concrete volume calculator
Concrete is ordered by volume with a waste allowance, and short-ordering a pour is far more expensive than over-ordering. Enter the element dimensions and quantity to get the volume in every unit a supplier might quote, plus the bag count for small hand-mixed pours.
concrete volume calculator
- Volume to order
- 3.78m³
- Net volume
- 3.6 m³ (127.13 ft³)
- Cubic yards
- 4.94yd³
- 25 kg bags (hand mix)
- 382 bags ≈ 9.07 t
Formula
volume = length × width × thickness × quantity × (1 + waste %)Assumes 2400 kg/m³ for normal-weight concrete and roughly 0.95 m³ of set concrete per m³ of dry mix. Deduct large openings and column heads separately rather than averaging thickness.
Worked examples
| Input | Result |
|---|---|
| 6 × 4 m slab at 150 mm | 3.6 m³ net, 3.78 m³ ordered at 5% waste |
| 10 pad footings 1 × 1 × 0.6 m | 6.0 m³ net, 6.3 m³ ordered |
| 300 × 300 mm column, 3 m tall | 0.27 m³ each |
Questions
How much waste should I allow on a concrete order?
5% for a clean slab on a level formation, up to 10% for footings on uneven ground or pours with heavy reinforcement congestion. Confirm the supplier's minimum load and part-load charge before trimming the figure.
How many 25 kg bags make a cubic metre?
Roughly 100–110 bags of dry mix per cubic metre of placed concrete. Anything above about 0.5 m³ is cheaper and far more consistent as a ready-mix delivery.
Can I take this quantity from a Revit model?
Yes — schedule the structural element volume parameter rather than deriving it from dimensions, then add the waste allowance outside the model. Model volume is net and excludes formwork tolerance and spillage.
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