Work out the cement, sand and aggregate (ballast) quantities for a concrete mix by volume and ratio.
Enter the length, width and depth of the area to be filled, then choose the mix ratio (cement : sand : aggregate) that suits the job. The tool splits your total volume into the dry quantities of each ingredient, adding an allowance because dry materials shrink when water is added — you always need more dry volume than the finished wet volume.
| Ratio | Strength | Use |
|---|---|---|
| 1:2:4 | Standard | Paths, bases, general slabs |
| 1:1.5:3 | High | Footings, structural slabs |
| 1:3:6 | Low | Mass fill, backfill |
A 2 m × 2 m base at 100 mm deep = 0.4 m³. For a 1:2:4 mix that needs roughly 0.28 m³ aggregate, 0.14 m³ sand and 90 kg cement, once the shrinkage allowance is applied. In US units, 0.4 m³ ≈ 14 ft³ ≈ 0.52 yd³.
Tip: measure aggregate (called “gravel” or “ballast”) and sand by volume with the same bucket to keep the ratio consistent.
A 1:1.5:3 mix (one part cement, one and a half parts sand, three parts aggregate) gives a strong structural concrete suitable for footings and slabs.
Yes. Combine the sand and aggregate figures — ballast is simply pre-mixed sand and gravel. Use roughly four parts ballast to one part cement for a general mix.
For a 1:2:4 mix you need roughly 300 kg of cement (about 12 bags of 25 kg) per cubic metre.
A 1:2:4 mix (cement : sharp sand : aggregate) is a common general-purpose ratio. For stronger structural work a 1:1.5:3 mix is often used.
Roughly half the weight of the cement (a water-cement ratio around 0.5). Add it gradually — the mix should be workable but not sloppy.
