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Known m³ → mix quantities
Split a known finished volume into cement, sharp sand, coarse aggregate and water.
Which calculator should I use?
Mix inputs
m³
%
part
part
part
kg
L
Enter the actual finished output made in one batch, not the mixer's total drum capacity.
Detailed assumptionsDry-volume factor, bulk densities and measure
×
L
kg/m³
kg/m³
kg/m³
Bulk density includes the air spaces between loose particles. Replace the defaults if your material supplier provides measured data.
Indicative result
Calculated concrete volume
1.00 m³
Ratio by volume 1 : 2 : 3 · waste 0%
Cement
350 kg
14 bags × 25 kg
0.25 m³ · 25 × 10 L buckets
Sharp sand
800 kg
0.50 m³
50 × 10 L buckets
Gravel or crushed stone
1,088 kg
0.75 m³
75 × 10 L buckets
Indicative mixing water
154–182 L
Start at about 154 L
Damp aggregates already contain water.
For one full 100 L batchusing the selected ratio
Cement35 kg
Sharp sand80 kg
Coarse aggregate109 kg
Water15–18 L
Calculation breakdown
1.00 m³ × 1.50 ÷ 6 parts
The water figure is not an exact “add it all” instruction. Start at the lower end and add water gradually. Excess water can reduce strength and durability.
Check the input values
One or more values are invalid.
From volume to materials
How do I use the concrete mix ratio calculator?
Use this tool when the finished concrete volume is known and you plan to make a small quantity from separately purchased constituents.
Enter the finished concrete volume
Use the volume specified for the work or obtained from the Concrete Calculator. The default waste allowance is 0%.
Select a ratio by volume
Measure every dry constituent with the same container. A 1:2:3 ratio means volume, not kilograms.
Check your materials
Bulk density and moisture vary. Enter supplier data in the detailed assumptions when available.
Add water gradually
Start at the lower end of the displayed range. Account for damp aggregates and aim for a workable mix that can be properly compacted.
Common question
How much cement, sand and aggregate are needed for 1 m³ of concrete?
This example uses a 1:2:3 ratio by volume, a 1.50 dry-volume factor and the calculator's default bulk densities. It is an estimate, not a verified mix design.
| Constituent | Volume part | Loose volume | Estimated mass | Practical measure |
|---|---|---|---|---|
| Cement | 1 part | 0.25 m³ | about 350 kg | 14 bags × 25 kg |
| Sharp sand | 2 parts | 0.50 m³ | about 800 kg | 50 buckets × 10 L |
| Gravel or crushed stone | 3 parts | 0.75 m³ | about 1,088 kg | 75 buckets × 10 L |
| Water | based on cement | — | about 154–182 kg | 154–182 L, added gradually |
What does a 1:2:3 concrete mix mean?
A 1:2:3 mix means one volume part cement, two parts suitable sharp sand and three parts coarse aggregate. The same 10 litre bucket can be used for all three dry constituents.
Shovels are not consistent measures because each load can vary. For small batches, use one bucket or gauge box throughout.
Why is a larger dry-material volume calculated?
Loose sand and coarse aggregate contain air voids. During mixing and compaction, cement and smaller particles fill some of them, so the sum of loose dry volumes must be greater than the target finished volume.
The calculator default is 1.50. Actual yield depends on grading, moisture, batching accuracy and compaction.
How much water should be added to concrete?
The water/cement ratio strongly affects strength, porosity and durability. The displayed range corresponds to 11–13 litres per 25 kg of cement, but it is only a starting guide.
Damp sand and aggregate already contribute water, so start low. Add small amounts only as needed for mixing, placing and proper compaction.
Does a volume ratio determine concrete strength class?
No. A simple ratio does not verify C16/20, C20/25 or any other class. Cement type, aggregate grading and moisture, actual water/cement ratio, mixing, compaction and curing all affect performance.
For structural or specified work, use the project mix specification or appropriately supplied ready-mixed concrete. The preset labels are not strength classes.
Mixing concrete in a mixer
Practical sequence for a small batch
Follow the instructions supplied with the cement, additions and mixer. The sequence below is general guidance only.
- 1Prepare one consistent measure
Batch with a bucket or gauge box rather than inconsistent shovels. Prepare all constituents before starting.
- 2Combine the dry constituents
Distribute cement evenly through the sand and coarse aggregate without leaving dry lumps.
- 3Add water in stages
Do not add the whole range at once. Allow for aggregate moisture and monitor workability.
- 4Place and compact
Place the mixed concrete without unnecessary delay and compact it properly to remove large air voids.
- 5Cure the concrete
Protect it from rapid drying, frost and excessive heat, and follow the curing requirements for the work.
Choose the appropriate supply method
Mix on site or order ready-mixed concrete?
Site mixing
Practical for small quantities, isolated post holes, repairs or areas a delivery vehicle cannot reach. It needs storage space, consistent batching and enough time for every batch.
Ready-mixed concrete
Normally more suitable for larger continuous pours, structural work and jobs with specified strength, consistency or exposure requirements.
Sources and calculation limits
Ratios are indicative values for small-volume batching. The dry-volume factor and bulk densities are editable starting assumptions. This tool does not verify concrete strength class or replace a specified mix design.
Work safely with cement and wet concrete
Cement dust irritates the respiratory system, while wet cement and concrete can cause dermatitis and serious chemical burns. Wear suitable waterproof gloves, eye protection and protective clothing, and follow the safety data sheet.
HSE guidance on cement safetyFrequently asked questions about concrete mix ratios
Answers about 1:2:3 mixes, cement bags, water, aggregates and site mixing.
These are volume parts: one equal measure of cement, two of sharp sand and three of coarse aggregate. It is not a ratio by weight and does not guarantee a concrete strength class.
Using the default 1:2:3 volume ratio, 1.50 dry-volume factor and cement bulk density of 1,400 kg/m³ gives about 350 kg of cement, or fourteen 25 kg bags. Other ratios and material properties give different results.
Under the default 1:2:3 assumptions, 25 kg of cement with the calculated sand, coarse aggregate and water gives roughly 70 litres of finished concrete. This is an indicative yield.
The initial guide is about 11–13 litres of water per 25 kg of cement. Start at the lower end and add gradually because damp aggregates contribute water. Excess water can reduce strength and durability.
Moisture on and within sand and aggregate becomes part of the mix water. Adding the full estimate without allowing for it can make the actual water/cement ratio too high.
No. Cement type, aggregate grading and moisture, water/cement ratio, mixing, compaction and curing all affect performance. Structural work needs a specified and verified mix.
Ballast is an all-in aggregate containing fine and coarse material. This calculator assumes sand and coarse aggregate are measured separately; when using ballast, follow the cement-to-ballast ratio and yield stated by the supplier.
Ready-mixed concrete is normally preferable for larger continuous pours, structural work and specified strength or exposure requirements. Site mixing is more practical for small, non-critical jobs.
Loose materials contain air voids. Mixing and compaction allow smaller particles to fill some of them, so finished concrete occupies less volume than the separately measured dry constituents.
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