Work out the concrete volume for a slab, a set of post holes or a circular pad before you order. Enter the dimensions in metric or imperial; Chippy Tools shows the calculated volume and a total with a 10% wastage allowance.
The calculator works offline on iPhone and Android. Use the dimensions from your actual job and check the final order with your concrete supplier.
Concrete Slab Calculator
Open Concrete Quantities and enter the slab’s length, width and depth. When using imperial measurements, tap Calculate to see the result.
Metric example
A slab 6 m long × 4 m wide × 100 mm deep has a volume of:
6 × 4 × 0.1 = 2.4 m³
With a 10% allowance, the estimate becomes 2.64 m³. Convert the depth from millimetres to metres before multiplying.
Imperial example
A slab 12 ft long × 10 ft wide × 4 in deep has a volume of:
12 × 10 × (4 ÷ 12) = 40 ft³, or approximately 1.48 yd³.
With a 10% allowance, that is 44 ft³, or approximately 1.63 yd³. Confirm the supplier’s ordering increments before arranging delivery.
Post Hole Concrete Calculator
Open Concrete Quantities, select Holes, and enter the hole depth, width and number of holes. Use consistent dimensions for each group of holes; calculate groups separately if their sizes differ.
For a manual check of a circular hole, use π × radius² × depth. Account for the volume displaced by the post when estimating how much concrete will fill the remaining space.
Circular Concrete Slabs Calculator
Open Concrete Quantities, select Circular Slabs, and enter the depth and width. The radius used in the volume formula is half the pad’s diameter.
The same principles apply as for a rectangular slab: use consistent units, measure the actual dimensions, and allow for waste appropriate to the job.
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