Home & Construction Calculators
Estimate cement, sand, coarse aggregate and mixing water from a preset or custom nominal concrete ratio. The result includes volumes, weights, cement bags and material cost.
Concrete mix ratio formula
Dry volume = adjusted wet volume × dry-volume factor
Ingredient volume = dry volume × ingredient parts ÷ total parts
Ingredient weight = ingredient volume × bulk density
Water = cement weight × water-cement ratio
The dry-volume factor accounts for voids and volume reduction when separate dry ingredients are combined and compacted. A value near 1.54 is often used for preliminary nominal-mix estimates, but actual yield depends on materials, grading, moisture and batching.
Worked example: 1 : 2 : 4
For 1 m³ of finished concrete with 5% allowance and a 1.54 dry factor, estimated dry ingredient volume is 1.617 m³. The seven total ratio parts allocate about 0.231 m³ cement, 0.462 m³ sand and 0.924 m³ aggregate. With the sample bulk densities, cement is about 333 kg, or seven 50 kg bags when rounded up.
What the ratio means
A 1 : 2 : 4 ratio means one equal volume part cement, two parts sand and four parts coarse aggregate. It does not directly state concrete strength, slump, durability or maximum water content.
Planning checklist
- Use the same measuring container for every ratio part.
- Account for moisture and bulking in site sand.
- Use clean, correctly graded aggregate.
- Do not add water only to improve workability.
- Confirm bag mass; common sizes vary by market.
- Use trial batches or an approved design for important work.
Water-cement ratio
The water-cement ratio is water mass divided by cement mass. Lower values can improve strength and durability when consolidation and curing are adequate, but the correct value depends on the design and admixtures.
Frequently asked questions
Is 1 : 2 : 4 suitable for every project?
No. It is a familiar nominal ratio for general estimating, but structural and exposure-critical concrete requires a specified or engineered mix.
Why are cement bags rounded up?
Cement is purchased in whole bags. The calculator shows the exact cement mass and rounds the bag count upward.
Does cost include labor and delivery?
No. The cost result covers only the three entered material prices. Add water, admixtures, labor, equipment, delivery and tax separately.
Can I use cubic yards?
Yes. The entered finished volume is converted internally to cubic meters, and results also show cubic feet and cubic yards.
Common mistakes
- Applying the ratio directly to wet volume without a yield factor.
- Confusing volume proportions with weight proportions.
- Using wet sand volume without moisture correction.
- Assuming a nominal ratio guarantees strength.