This concrete mix ratio calculator turns a mix ratio and the volume you need into the amount of cement, sand, and gravel to buy. Enter your ratio and target volume above to get bags and material quantities.
How to use this calculator
- Enter the concrete volume you need (cubic feet or yards).
- Enter the mix ratio — cement : sand : gravel (e.g. 1:2:3).
- Read the cement bags, sand, and gravel required.
How is the concrete mix calculated?
Dry materials bulk up, so multiply the wet volume by ~1.54, then split by the ratio parts:
Dry volume = Wet volume × 1.54 Sum of parts = cement + sand + gravel Cement = Dry volume × (cement part ÷ sum) Sand = Dry volume × (sand part ÷ sum) Gravel = Dry volume × (gravel part ÷ sum)
Example calculation
For 1 cubic yard (27 ft³) at a 1:2:3 ratio:
- Dry volume = 27 × 1.54 = 41.6 ft³
- Cement = 41.6 ÷ 6 = 6.9 ft³ → about 7 bags (94 lb)
- Sand = 13.9 ft³, Gravel = 20.8 ft³
- Water at a 0.5 ratio ≈ 39 gallons
Common mix ratios
- 1:2:3 — general-purpose slabs, footings, steps.
- 1:1.5:3 — stronger structural work (~M20/3000 psi).
- 1:3:6 — non-structural fill and mass concrete.
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Frequently Asked Questions
What is the standard concrete mix ratio?
A common general-purpose ratio is 1:2:3 — one part cement, two parts sand, three parts gravel. Stronger structural mixes use 1:1.5:3 (about M20).
How many bags of cement are in a cubic yard?
At a 1:2:3 ratio, roughly 7 bags of 94-lb cement go into one cubic yard of concrete, once you allow for the dry-volume bulking factor.
Why multiply by 1.54?
Dry cement, sand, and gravel occupy more space than the finished wet concrete. Multiplying the wet volume by about 1.54 accounts for that shrinkage when you buy materials.