Concrete Mix Ratio Calculator
Work out exactly how much cement, sand, aggregate and water you need for any concrete mix ratio. Enter your pour volume and get precise bag counts in seconds.
Pour & Mix Details
Enter your concrete volume and mix ratio to get exact material quantities
Total wet, compacted volume of concrete you need to pour.
Choose a standard nominal mix, or select custom to enter your own parts.
Allowance for voids and bulking when converting wet volume to loose dry materials. 1.54 is standard.
Weight of a single bag of cement.
Weight of water as a proportion of cement weight. 0.45–0.55 is typical.
Material Quantities
Cement, sand, aggregate and water needed for your pour
Enter your concrete volume and mix ratio above, then click Calculate Material Quantities to see how much cement, sand and aggregate you need.
Standard Nominal Mix Ratios
Nominal mixes are pre-set cement:sand:aggregate proportions used for everyday concrete work where a lab-designed mix isn’t required. Pick the closest strength grade to your project below.
| Mix Ratio | Grade | Typical Use |
|---|---|---|
| 1 : 1 : 2 | M25+ | Heavy-duty slabs, columns, high-strength structural work |
| 1 : 1.5 : 3 | M20 | Reinforced foundations, structural beams and columns |
| 1 : 2 : 4 | M15 | Driveways, footpaths, domestic slabs and footings |
| 1 : 3 : 6 | M10 | Mass concrete fill, non-structural foundations |
| 1 : 4 : 8 | M7.5 | Blinding layers, oversite concrete |
| 1 : 5 : 10 | M5 | Lean mix bedding, levelling courses |
Concrete Mix Ratio FAQ
Everything you need to know about mix ratios, dry volume factors, and getting your quantities right before you order materials.
A concrete mix ratio describes the proportions of cement, sand and coarse aggregate used in a mix, written as cement:sand:aggregate, such as 1:2:4. Common nominal mixes range from 1:1.5:3 for structural work to 1:5:10 for mass concrete and blinding.
For a standard 1:2:4 mix, you need roughly 320kg of cement per cubic metre of finished concrete, which works out to around 6.4 bags at 50kg each. The exact figure depends on the mix ratio you choose and the dry volume factor used in the calculation.
Wet, compacted concrete takes up less space than the loose dry materials that make it, because sand and aggregate contain air voids that get filled once cement paste and water are added. A factor of around 1.54 is the standard allowance used to convert a finished wet volume back into the loose dry volume of cement, sand and aggregate needed.
Most domestic slabs, driveways and footings use a 1:2:4 mix, roughly equivalent to M15 to M20 strength grades. Foundations carrying heavier loads or exposed to vehicle traffic often move to a 1:1.5:3 mix for extra strength, while mass fill or blinding layers can use a leaner 1:3:6 or 1:4:8 mix.
Divide a volume in cubic feet by 35.32 to get cubic metres. For a slab, multiply length by width by thickness in metres to get the wet volume directly, then feed that figure into a mix ratio calculator to find material quantities.