Concrete Mix Calculator
This concrete mix calculator works out the cement, sand, and gravel you need for a given volume and ratio. As a cement calculator it supports common recipes like the 1:2:4 concrete mix, allowing for the dry-to-wet shrinkage so your materials make the finished volume of ready mix concrete you actually need.
How to use this calculator
- Enter the finished volume of concrete you need.
- Pick a mix ratio — 1:2:4 is a good all-purpose choice.
- Read the cement bags and the sand and aggregate volumes.
- Buy a little extra of each to allow for spillage and measuring loss.
The formula
Dry materials lose volume when mixed, so multiply the finished volume by about 1.54 to get the dry volume, then split it by the ratio parts. A 94 lb bag of cement is roughly 1 cubic foot:
Dry volume = Wet volume × 1.54; each material = Dry volume × (part ÷ total parts)
Worked example. One cubic yard (27 ft³) at 1:2:4: dry volume is 27 × 1.54 = 41.6 ft³, split into 7 parts. Cement is 1 part = 5.9 ft³ ≈ 6 bags, sand is 2 parts ≈ 11.9 ft³, and aggregate is 4 parts ≈ 23.8 ft³.
Frequently asked questions
What is a 1:2:4 concrete mix?
It means 1 part cement, 2 parts sand, and 4 parts coarse aggregate by volume. A 1:2:4 mix is a common general-purpose recipe that reaches roughly 3,000 psi.
How much cement, sand, and gravel do I need per cubic yard?
For a 1:2:4 mix, about 6 bags of cement, 0.44 cubic yards of sand, and 0.88 cubic yards of gravel make a cubic yard of concrete, allowing for the dry-to-wet volume shrinkage.
Why is dry material more than the finished volume?
Dry sand and aggregate have air gaps that fill in when mixed and compacted. This calculator multiplies the wet volume by about 1.54 to account for that bulking.
Which concrete mix ratio is strongest?
Lower aggregate ratios are stronger. A 1:1.5:3 mix reaches about 4,000 psi, while a leaner 1:3:6 mix is weaker and used for non-structural fill.