BuildCalc

Concrete Mix Ratio Calculator

Mixing your own concrete from cement, sand and stone? Choose a nominal mix ratio and enter the volume you need — the calculator returns the sacks of portland cement, the cubic feet of sand and coarse aggregate, and the water for a 0.50 water-cement ratio.

Cement needed
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    How it works

    Dry ingredients occupy more space than the finished concrete, because sand fills the voids between the stones and cement paste fills the voids between the sand. The standard allowance is a dry volume about 1.54 times the wet volume. Each material is then its share of the ratio: for 1:2:4 the parts total 7, so cement is one seventh of the dry volume. A US sack of portland cement is 94 lb and measures about 1 cubic foot, and water is taken at a 0.50 water-cement ratio by weight.

    Frequently asked questions

    What is the correct concrete mix ratio?

    For most general work, 1 part cement to 2 parts sand to 4 parts coarse aggregate by volume gives roughly 3,000 psi. Richer 1:2:3 is used where more strength is wanted, and lean 1:3:6 suits footings and mass fill.

    How much cement do I need per cubic yard?

    A 1:2:4 mix works out at about 5.9 sacks of 94 lb cement per cubic yard, and a richer 1:2:3 at about 6.9 sacks. Enter your dimensions above for the exact figure for your pour.

    Why multiply the volume by 1.54?

    Loose dry materials contain air voids that disappear once mixed and compacted, so you always need more dry volume than the finished concrete occupies. The 1.54 factor is the standard allowance for that shrinkage — it typically ranges from 1.52 to 1.57.

    How much water goes into a concrete mix?

    Around 0.45 to 0.55 parts water to one part cement by weight. Lower is stronger but harder to place. This calculator uses 0.50, so a 94 lb sack of cement takes about 47 lb of water — roughly 5.6 gallons.

    Should I mix my own or buy pre-mix bags?

    Mixing from raw materials is cheaper per cubic yard and lets you control the mix, but it needs accurate batching to be consistent. For small pours, bagged pre-mix is far more reliable. For anything over about a cubic yard, ready-mix beats both.

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    Estimates are for planning only. Material yields, densities and code requirements vary — confirm quantities with your supplier and local building code before ordering.