Concrete Calculator
Rectangle or circle, thickness in inches/feet or mm/cm/m, waste allowance, and both bagged and ready-mix estimates side by side.
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Concrete & Masonry
Concrete is ordered by volume, and volume is where most DIY estimates go wrong — a slab 10 × 6 ft and 4 inches thick is already 0.74 cubic yards. The tools below handle the math for rectangular and round pours.
Start with the calculator
What you can calculate
- Volume of rectangular slabs and square pads in cubic feet, cubic yards, and cubic metres at once.
- Round pours — pad footings and circular slabs — from diameter and thickness.
- Bag count using the yield printed on your chosen bag, and the bagged cost.
- Ready-mix volume and cost in cubic yards (or cubic metres) at your supplier's price.
Volume in plain terms
One cubic yard is 27 cubic feet — a box 3 × 3 × 3 ft. Suppliers sell wet concrete by the cubic yard; bags are labelled by the volume of mixed concrete each one yields. The calculator always shows all three units so you can compare against either kind of packaging.
Bagged or ready-mix?
- Bags suit small pours. Post footings, short walkways, and repairs — roughly up to about half a cubic yard, before hand-mixing 30+ bags loses its appeal.
- Ready-mix suits everything bigger. Trucks deliver by the cubic yard; small orders usually carry short-load fees, so ask your local plant.
- Estimate both, order one. The calculator keeps the two options separate — they are alternatives, never additions.
Structural concrete, reinforcement, foundations, and any load-bearing design require assessment by a qualified engineer or professional. These tools are for planning small non-structural projects only.
Guides for concrete projects
- How to Calculate Concrete Volume — the manual method with worked examples.
- Concrete Bags vs Ready-Mix — choosing the right supply method.
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- Flooring Calculator — planning a floor over the pad?
- Paint Calculator — for the walls that will surround it.