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Concrete calculator

Work out how much concrete a slab, patio or footing needs, in cubic yards, cubic meters and premix bags.

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Cubic yards 1.36 yd³

How it works

volume = length × width × thickness

A slab is a flat box, so its volume is length × width × thickness. Everything is changed to meters first, so the answer comes out in cubic meters, then into cubic yards (what US ready-mix is sold by) and premix bags. Add some extra for spillage, uneven ground and forms that bow: 5–10% is usual.

  1. Multiply length × width × thickness (in meters) 3.048 × 3.048 × 0.1016 × 1 = 0.944 m³
  2. Add the extra for waste 0.944 × (1 + 10 ÷ 100) = 1.04 m³
  3. Change to cubic yards 1.04 ÷ 0.764554858 = 1.36 yd³
  4. Count the 80 lb bags (0.6 ft³ each), rounding up 36.67 ÷ 0.6 = 61.11 → 62

Premix bag yields

Bag Makes about
40 lb (18 kg) 0.30 ft³ (8.5 L)
60 lb (27 kg) 0.45 ft³ (12.7 L)
80 lb (36 kg) 0.60 ft³ (17 L)

Typical yields printed on US premix bags; check the bag you buy.

Printed from rocketcalc.io/construction/concrete