Calculators/ Concrete/Concrete Mix Ratio Calculator
Concrete Mix Ratio Calculator
Cement, sand and aggregate for a mix-your-own batch.
Concrete Mix Ratio Calculator
ft³
%
Mixing your own concrete means buying three materials separately in the right proportions. The catch is that dry ingredients occupy about 54 percent more volume than the finished concrete, because the cement paste fills the voids between the aggregate.
How this is calculated
- Multiply the finished volume by 1.54 to get the dry volume needed. This is the step most people miss.
- Split the dry volume by the ratio parts. A 1:2:3 mix has six parts, so cement is one sixth of the dry volume.
- One 94 lb bag of Portland cement is approximately one cubic foot.
- Keep the water-cement ratio near 0.5 by weight. More water is easier to place and permanently weaker.
Frequently asked questions
What is the strongest concrete mix ratio?
For hand mixing, 1:1:2 gives the highest strength but is harsh to work and expensive in cement. 1:2:3 is the usual general purpose compromise at around 3,000 psi.
Why multiply by 1.54?
Dry sand and aggregate have air voids between the particles. Once mixed with cement paste and water, those voids fill and the total volume drops by about a third.