Concrete
Quick answer: A 10 × 0.4 × 0.5 m strip footing needs about 2.1 m³ of C25/30 concrete: about 735 kg of cement (30 bags), 2.7 m³ of aggregate and 378 L of water.
Calculate concrete volume and materials
How the calculation works
Add elements (footing, slab, beam, column), enter dimensions and quantity, then pick the concrete class and reserve. The calculator adds up the volumes, applies the reserve, and estimates mass and ingredients for hand mixing.
Formula and assumptions
Volume = length × width × height (round: π × r² × height), summed over all elements. Volume with reserve = volume × (1 + reserve). Mass ≈ volume × 2400 kg/m³. Ingredients per concrete class, e.g. C25/30 = 350 kg cement, 0.5 m³ sand, 0.8 m³ gravel and 180 L water per m³; cement in 25 kg bags, rounded up. Mixes are indicative – structural concrete follows the design and the supplier.
Worked example
Strip footing 10 × 0.4 × 0.5 m = 2 m³; 5 % reserve → 2.1 m³. C25/30: cement 350 × 2.1 = 735 kg → 30 bags × 25 kg; aggregate (0.5 + 0.8) × 2.1 = 2.73 m³; water 180 × 2.1 = 378 L.
More worked examples
- Slab 5 × 4 × 0.12 m = 2.4 m³; reserve 5 % → 2.52 m³. C25/30: cement 350 × 2.52 = 882 kg → 36 bags of 25 kg; aggregate (0.5 + 0.8) × 2.52 = 3.28 m³; water 180 × 2.52 = 454 L.
- Round column Ø 0.4 m, height 3 m: π × 0.2² × 3 = 0.377 m³; reserve 5 % → 0.396 m³. C25/30: cement 350 × 0.396 = 138.6 kg → 6 bags; water about 71 L.
Cubic metres and ingredients for C25/30 by element and volume (no reserve)
| Volume (m³) | Cement (kg) | Bags of 25 kg | Sand (m³) | Gravel (m³) | Water (L) |
|---|---|---|---|---|---|
| 0.2 (1 m of strip footing 40 × 50 cm) | 70 | 3 | 0.1 | 0.16 | 36 |
| 0.252 (column 30 × 30 × 280 cm) | 88.2 | 4 | 0.13 | 0.2 | 45 |
| 1 (slab 10 m² × 10 cm) | 350 | 14 | 0.5 | 0.8 | 180 |
| 1.2 (slab 10 m² × 12 cm) | 420 | 17 | 0.6 | 0.96 | 216 |
| 1.5 (slab 10 m² × 15 cm) | 525 | 21 | 0.75 | 1.2 | 270 |
| 2 | 700 | 28 | 1 | 1.6 | 360 |
| 5 | 1750 | 70 | 2.5 | 4 | 900 |
| 10 | 3500 | 140 | 5 | 8 | 1800 |
| 20 | 7000 | 280 | 10 | 16 | 3600 |
What affects real consumption
- Excavation and formwork irregularities increase the real volume.
- Losses in transport, pumping and spillage.
- Aggregate moisture and consistency change the water needed.
Common mistakes
- Leaving out the reserve, so the last pour runs short.
- Treating the indicative recipes as valid for structural concrete; the design and the supplier decide.
- Mixing up volume and weight: 1 m³ of concrete weighs about 2400 kg.
Frequently asked questions
How do I calculate cubic metres of concrete?
Multiply length × width × thickness in metres (divide centimetres by 100): a 5 × 4 m slab 12 cm thick = 5 × 4 × 0.12 = 2.4 m³. Add up the volumes of all elements. The calculator then adds the chosen reserve (5 % by default) → 2.52 m³ and rounds the order up to 0.1 m³ → 2.6 m³.
How much spare concrete should I order?
5–10 % is typical depending on irregularities and placing method; you choose the reserve in the calculator.
Can hand-mixed concrete be used for structural elements?
Structural elements follow the design and quality requirements; ready-mix concrete delivers a controlled strength class.
How much cement per m³ of C25/30?
350 kg per m³, which is 14 bags of 25 kg.
How much does 1 m³ of concrete weigh?
About 2400 kg, which is the value the calculator uses for the mass.
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Publisher: Art-Visum d.o.o. · Content reviewed:
Calculations use common consumption rates and manufacturers' technical data sheets; results are estimates. Methodology · Standards · About · Worked example