About this calculator
Use this calculator to work out how much concrete fills a slab, footing, column or beam. It gives the geometric (theoretical) volume and, if you enter a wastage allowance, a larger figure for planning orders. It does not assume a mix ratio and does not calculate cement, sand or aggregate — those depend on the specified mix design.
Formula
Slab / footing
V = L × W × T × n
Rectangular column
V = a × b × h × n
Circular column
V = π × d² ÷ 4 × h × n
Beam
V = length × width × depth × n
Worked example
- Slab 5 m × 4 m × 150 mm: 5 × 4 × 0.15 = 3.00 m³ (105.9 ft³). With 5% wastage: 3.00 × 1.05 = 3.15 m³.
- Rectangular columns, 4 × (300 × 450 mm, 3 m high): 0.30 × 0.45 × 3 × 4 = 1.62 m³.
- Circular columns, 6 × (Ø300 mm, 3 m high): π × 0.30² ÷ 4 × 3 × 6 = 1.272 m³.
- Beams, 2 × (6 m × 230 mm × 450 mm): 6 × 0.23 × 0.45 × 2 = 1.242 m³.
Assumptions and limitations
- Geometric volume of solid shapes at the dimensions entered. Volume taken up by reinforcement is ignored (it is normally small).
- Where beams, columns and slabs meet, make sure each overlapping part is counted only once.
- The volume ordered from a supplier may need to be larger than the geometric volume because of uneven formwork or ground, spillage and pump losses. Agree the order quantity with your supplier.
- This calculator does not design concrete or choose a mix. Structural concrete must follow the drawings and specification from a qualified engineer.
References
- Volume formulas for rectangular prisms and cylinders.