Metric Unit Calculator
The formula, your substituted values, and the evaluated result are shown below.
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View offerAffiliate link — we may earn a commission at no extra cost to you.Estimate cement requirements from area and coverage.
This is a planning estimate. Confirm dimensions, allowances, material specifications, applicable codes, and supplier requirements before purchasing or construction.
Estimate cement requirements from area and coverage.
The calculator divides the area you are covering by the coverage of one unit, then adds waste:
Units = area (m²) ÷ coverage per unit (m²) × (1 + waste % ÷ 100)
Use it for jobs measured by area, such as floor screeds, renders and toppings, where you know how far one bag goes. The answer isn't rounded, so round up to whole bags.
Cement is only one ingredient, so work out coverage from the mix: 1. A 1 : 4 cement-to-sand screed uses roughly 320 kg of cement per cubic metre of mortar. 2. A 25 mm screed is 0.025 m³ per square metre, so it needs about 0.025 × 320 = 8 kg of cement per m². 3. A 20 kg bag of cement therefore covers about 20 ÷ 8 = 2.5 m² at 25 mm.
| Use | Cement : sand (by volume) |
|---|---|
| Floor screed | 1 : 3 to 1 : 5 |
| External render | 1 : 4 to 1 : 5 (often with lime) |
| Bedding mortar for pavers | 1 : 4 to 1 : 6 |
These are general figures. Use the mix in your plans or the product specification, especially for wet areas under waterproofing.
For concrete slabs and footings, work out the volume with the concrete calculator. A typical general-purpose concrete uses about 300–350 kg of cement per m³, or buy premixed bags or ready-mix instead.
At 25 mm thick with a 1 : 4 mix, about 8 kg of cement per m², or 0.4 of a 20 kg bag.
At 12 mm thick with a 1 : 4 mix, allow roughly 4 kg of cement and 0.015 m³ of sand per square metre.
Cement is the binder powder. Concrete is cement mixed with sand, coarse aggregate and water. Mortar is cement, sand and water, often with lime.