Concrete Mix Ratio Calculator — Cement, Sand & Aggregate
Turn a concrete volume and mix ratio such as 1:2:4 or 1:1.5:3 into bags of cement, sand and gravel volumes and mixing water, using the dry-volume method.
Estimate ingredient quantities from a chosen loose-volume ratio of cement, sand and coarse aggregate. Enter the finished concrete volume, a yield factor and bulk densities to calculate cement bags, loose sand and aggregate volumes, and a total free-water target. The result is a quantity estimate; a ratio alone cannot establish a concrete strength grade.
How to use this tool
- Enter the finished volume and its unit.
- Choose a ratio or enter custom cement, sand and aggregate parts.
- Choose the cement bag size.
- Enter the specified water ratio, trial-batch volume factor and measured loose bulk densities.
- Read the quantities, then account for material moisture and actual batch yield.
Formula
Dry volume = finished volume × factor; ingredient volume = dry volume × its parts ÷ total parts; cement mass = cement volume × bulk density; water target = cement mass × water ratio
The default factor 1.54 and densities 1,440/1,600/1,500 kg/m³ are adjustable estimating assumptions, not universal material constants. The factor represents loose ingredient volume per unit of finished concrete. Water is approximated as 1 kg per litre.
Example
For 1 m³ at 1:1.5:3, factor 1.54 and cement bulk density 1,440 kg/m³, cement occupies 0.28 m³ and weighs 403.2 kg. That is 8.064 bags of 50 kg, so buy 9 bags before additional waste. Sand is 0.42 m³, aggregate 0.84 m³, and the total water target at ratio 0.5 is 201.6 L.
Frequently asked questions
Does 1:1.5:3 guarantee M20 concrete?
No. Strength also depends on materials, water, air, compaction and curing. Use the specified mix and its verification results; this arithmetic cannot assign a strength class.
Are these ratios by mass?
No, they are loose-volume proportions. Bulk densities convert those separate volumes into estimated masses. A mass-based recipe must not be entered unchanged as a volume ratio.
Is the water result the amount to pour in?
It is the total free-water target for this cement-only model. Water already carried by aggregates and water absorbed by them must be accounted for when determining batch water.
Why change the volume factor?
Packing and material grading change actual yield. Measure trial-batch output and adjust the factor instead of treating 1.54 as guaranteed.
Sources
Last updated: 2026-10-30