Foundation Concrete Calculator

How is foundation concrete calculated?

The quantity of foundation concrete follows from the volume formula for the shape of the footing. With all dimensions in metres the result is in cubic metres.

• Pad footing: length × width × depth × quantity.
• Sloped pad footing: a straight block at the bottom with a part that tapers towards the column on top. The tapered part is h₂ / 6 × [a·b + (a + a₂)·(b + b₂) + a₂·b₂].
• Strip footing: total length × width × depth.
• Raft foundation: plan area × thickness.

Blinding concrete

The blinding layer under a footing extends a little beyond the base on every side. The calculator asks for that overhang and the thickness separately and reports the blinding volume and base area apart from the structural concrete. The two are usually different grades and are ordered separately.

Example

Six pad footings of 2 m × 1.6 m and 0.5 m deep need 2 × 1.6 × 0.5 × 6 = 9.6 m³ net. With 5 percent waste the order is 10.08 m³. A 10 cm blinding layer that extends 10 cm on each side covers 2.2 × 1.8 × 6 = 23.76 m² and takes 2.376 m³.

Limits

This is a quantity tool. Sizing the footing, bearing capacity and reinforcement belong to the structural design. Calculate tie beams, lift pits and stepped footings separately and add them up.