How this calculator works
Concrete and gravel are rectangular layers with a shared ordering allowance. A two-way grid counts runs at or below the entered maximum spacing, inside a centreline edge offset. Dividing total straight bar length by stock length gives only a theoretical minimum purchase count. The full perimeter is used for forms. Prices are editable CAD estimates, excluding labour, excavation and taxes unless included in your rates or fixed extras.
Formula
Concrete = L x W x slab thickness x (1 + waste); gravel = L x W x base thickness x (1 + waste); forms = 2(L + W); grid runs = ceil(clear perpendicular dimension / spacing) + 1; cost = sum(quantity x rate) + fixed extras.
Worked example
A 4 m by 2 m drive at 0.1 m concrete and 0.2 m gravel needs 0.8 m3 concrete, 1.6 m3 gravel and 12 m forms before waste. At $100/m3 concrete, $50/m3 gravel and $10/m forms, those items total $280.
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Frequently asked questions
Does the total include labour?
Only if you include labour in the rates or fixed extras. The default calculation is a four-component material budget.
Is the rebar stock count sufficient to order?
It is a lower bound by total length. A cutting and splice plan must add lap lengths, hooks, bends and unusable offcuts before ordering.
Does this specify a driveway thickness?
No. Enter the thicknesses and reinforcement specified for site conditions and vehicle loads. These example defaults are not a structural design.