Concrete & Mortar Mix Calculator
Pick a mix and the volume, and get the cement bags plus sand and aggregate tonnages for the job.
Uses the standard 1.54 dry volume factor (allowing for voids and water). Cement at 1,440 kg/m³ in 25 kg bags; sharp sand 1.6 t/m³, 20 mm aggregate 1.68 t/m³, soft sand 1.5 t/m³. Mortar quantities are an estimate, actual use varies with joint size and wastage.
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How to use the concrete calculator
Choose a mix and enter the finished (wet) volume, and the calculator gives you the cement in 25 kg bags plus the sharp sand and aggregate tonnages. It uses the standard dry volume method, wet volume multiplied by 1.54 to allow for the voids that fill during mixing.
A standard 1:2:4 mix returns about 13 bags of cement, 0.70 t of sharp sand and 1.48 t of aggregate per cubic metre, figures that match published trade tables. Add around 5, 10% for waste.
Frequently asked questions
How much cement, sand and aggregate for 1m³ of concrete?
For a 1:2:4 mix, roughly 13 bags of 25 kg cement (about 317 kg), 0.70 tonnes of sharp sand and 1.48 tonnes of 20 mm aggregate per cubic metre.
What is a 1:2:4 concrete mix?
One part cement to two parts sharp sand to four parts coarse aggregate by volume, roughly equivalent to C20 concrete.
How many 25kg bags of cement in a cubic metre?
For a 1:2:4 mix, about 13 bags of 25 kg cement per cubic metre. Stronger mixes use more; weaker mixes use less.
What mortar mix should I use for bricklaying?
A 1:5 or 1:6 cement to sand mortar suits most bricklaying and blockwork; a stronger 1:4 for engineering bricks.