What ConcreteCalc Calculates
ConcreteCalc converts measurements into an estimated wet concrete volume in cubic metres. Each calculator shows its formula and working so you can check the result instead of relying on a hidden answer.
Choose the calculator that matches the shape
Use the slab calculator for rectangular pours, the circular slab calculator for round pours, the post hole calculator when a post displaces part of a cylindrical hole, the footing calculator for repeated rectangular footings, and the column and pier calculator for solid round or square columns.
Volume comes before bags and price
Dimensions are converted to metres before the shape's volume is calculated. A user-selected allowance can then be added to the geometric volume. The allowance is not a building rule: it simply lets you account for measurement uncertainty, an uneven excavation or handling loss.
The bag estimate uses 108 20kg bags per cubic metre, matching Boral's published Concrete Mix product guide. Bag yields differ, so the final check must always be the instructions on the product you plan to buy. Displayed bag prices are an indicative retail range reviewed on 24 August 2026; they are not live quotes.
What the calculators do not decide
ConcreteCalc does not choose slab thickness, hole depth, footing size, concrete strength, reinforcement, drainage or permit requirements. Those are design decisions that depend on the load, soil, structure, location and approved plans. Enter dimensions from your project documentation or an appropriately qualified professional.
Transparent and independently checkable
Calculator inputs stay in your browser. The formulas, assumptions, rounding rules, pricing basis and primary sources are documented on the methodology and sources page. Learn more about the project on the About page or report a problem through Contact.