Concrete volume

Choose a slab, round columns or strip footing and enter metres. Slab volume is length × width × thickness; footing volume is length × width × depth; round columns use π × (diameter/2)² × height × count. Count is a whole number. Order volume is net volume × (1 + reserve/100). Zero reserve is allowed; 10% is an editable example, not a site recommendation.

The result updates as you edit and shows net and order volume, estimated concrete mass and two alternative bag counts. Mass uses order volume × entered concrete density. Open Density and bag yield to enter prepared litres per 25 kg/40 kg bag; litres ÷ 1000 gives m³. Each bag count rounds order volume/yield up independently. They are alternatives, not amounts to add together. Only tiny floating-point roundoff near an integer is corrected; actual remainder needs another bag.

The defaults 2400 kg/m³, 12 L and 18 L are examples, not universal product values. Use the concrete mixture’s density and prepared yield, not dry-powder bulk density or the bag mass divided by concrete density. For comparison, a Tarmac product data sheet lists 12.5 L per 25 kg and 2200–2300 kg/m³. The calculator does not select a mix, water addition, reinforcement or structural dimensions; it estimates material from the supplied geometry.

Inputs accept decimal comma or point. Dimensions, density and yields have software bounds 0.000001–1,000,000 in their displayed units; column count 1–10,000 and reserve 0–100%. Invalid dimensions or reserve hide the result. An invalid density or yield leaves only its corresponding estimate blank. Outputs outside the supported range are withheld. Reset restores the examples and closes assumptions. Small or very large nonzero values use scientific notation. The browser retains your inputs.