Build & renovate
Concrete Calculator
Length times width times depth, plus a wastage margin - then decide: bags for the small pour, a truck past one cubic metre.
Calculator
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How it works
Volume = L x W x depth. A 25 kg bag of ready-mix yields about 0.0125 m3, so a cubic metre is ~80 bags - which is why anything above ~1 m3 usually means ordering ready-mixed. Concrete weighs ~2.4 t/m3.
Frequently asked questions
How many 25 kg bags per cubic metre?
About 80 bags of pre-blended ready-mix (each yields ~0.0125 m3). That is two tonnes of bags to barrow - the practical argument for a mixer truck.
How thick should a shed base be?
100 mm is typical for sheds and paths on a sound sub-base; 150 mm for driveways. A 3 x 2 m shed base at 100 mm is 0.6 m3 - about 50 bags.