Cement, Sand & Aggregate Calculator

Use this cement sand aggregate calculator to turn a volume of wet concrete into cement bags, sand and coarse aggregate for a nominal mix such as 1 : 1.5 : 3 (M20). It also gives the water for your chosen w/c ratio.

With the default inputs, 1 m³ of M20 concrete with 2% wastage needs 411.3 kg of cement (8.23 bags of 50 kg, so buy 9), 0.428 m³ of sand, 0.857 m³ of aggregate and about 202 litres of water. The dry volume factor and material densities can be changed under Advanced.

How to use it

1. Enter the Concrete volume (wet) in m³.
2. Choose the Nominal mix (cement : sand : aggregate). Pick Custom ratio to type your own Cement part, Sand part and Aggregate part.
3. Select the Cement bag size: 50, 40, 25 or 20 kg, or 94 lb (US).
4. Set the Water–cement ratio and the Wastage allowance in percent.
5. If you have your own test figures, change the Dry volume factor, Cement bulk density, Sand bulk density or Aggregate bulk density. The results update as you type.

How the quantities are calculated

Loose dry materials take up more space than the concrete they make, because the voids between particles fill with paste. The tool scales the wet volume up by a dry volume factor (default 1.54) and the wastage, then splits it in the mix ratio c : s : a.

• Dry volume: Vdry = Vwet × (1 + wastage / 100) × 1.54
• Each material: Vdry × part / (c + s + a)
• Cement mass: cement volume × 1,440 kg/m³; bags = mass / bag size
• Sand and aggregate mass: volume × 1,600 and 1,500 kg/m³ (loose bulk densities)
• Water in litres: cement mass ÷ (1 + wastage / 100) × w/c ratio. Water follows the cement actually mixed, not the spare cement bought to cover wastage.

At 1,440 kg/m³, one 50 kg bag holds 0.0347 m³ of cement.

Worked example: 1 m³ of M20 (1 : 1.5 : 3) concrete

1. Dry volume: 1 × 1.02 × 1.54 = 1.571 m³ (1.5708).
2. Sum of parts: 1 + 1.5 + 3 = 5.5.
3. Cement: 1.5708 × 1 / 5.5 = 0.2856 m³; 0.2856 × 1,440 = 411.3 kg; 411.3 / 50 = 8.23 bags, so 9 bags.
4. Sand: 1.5708 × 1.5 / 5.5 = 0.428 m³, which is 0.69 t at 1,600 kg/m³ or 15.1 ft³.
5. Aggregate: 1.5708 × 3 / 5.5 = 0.857 m³, which is 1.29 t at 1,500 kg/m³ or 30.3 ft³.
6. Water at w/c 0.5: the cement actually mixed is 411.3 / 1.02 = 403.2 kg, and 403.2 × 0.5 = 201.6, shown as 202 litres.

Limits of this calculator

• These are traditional site volume ratios. IS 456:2000 allows nominal mixes only up to M20, so the 1 : 1 : 2 option (often called M25 on site) is for estimating only. Structural concrete to a specification needs a designed mix from a laboratory.
• Damp sand bulks, so a gauge box of wet sand holds less sand than the same box dry. Allow for bulking or batch by mass.
• The water figure ignores moisture already in the sand and aggregate. Cut the added water if the stockpiles are wet.
• 1,440, 1,600 and 1,500 kg/m³ are typical loose densities. If you buy sand or aggregate by the tonne, weigh a known volume of your own material and enter it.

Questions people ask

How many bags of cement are in 1 m³ of M20 concrete?

With a 1 : 1.5 : 3 mix, a dry volume factor of 1.54 and no wastage, 1 m³ of M20 needs 403.2 kg of cement, or 8.06 bags of 50 kg. With the default 2% wastage it is 411.3 kg (8.23 bags), so you would buy 9 bags.

Why is the dry volume factor 1.54?

Dry cement, sand and aggregate contain voids that close up once water is added and the concrete is compacted, so you need more loose material than the finished volume. Site estimates use a factor of about 1.52 to 1.57, and 1.54 is the usual choice. You can change it under Advanced.

How much sand and aggregate do I need for 1 m³ of M15 concrete?

For a 1 : 2 : 4 mix with no wastage, 1 m³ of M15 needs 0.44 m³ of sand and 0.88 m³ of coarse aggregate. It also needs 316.8 kg of cement, which is 6.34 bags of 50 kg. These use the same 1.54 dry volume factor as the tool.

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Results are for estimating, checking and learning. Design work should be checked against the current code and your project specification, and signed off by a qualified engineer. See all 20 engineering calculators.