Cement Calculator
Cement bags = wet volume × 1.54 for the dry materials, × the cement share of the mix ratio, × 1,440 kg/m³ ÷ 50 kg. A 10 × 10 ft slab 4 in thick at 1:2:4 needs about 6 bags, 7 with 5% waste, plus 0.415 m³ of sand and 0.830 m³ of aggregate. For ready-mix, use the Concrete Calculator.
How it's calculated: Dry volume = wet volume × 1.54; cement = dry volume × cement part ÷ total parts; bags = cement m³ × 1,440 kg/m³ ÷ 50 kg.
Result appears here
Fill in the fields and press Calculate.
Formula, calculation, assumptions and sources
Dry volume = (L × W × D) × 1.54
Cement volume = Dry volume × cement-part ÷ (sum of parts); bags = cement volume × 1,440 kg/m³ ÷ 50
Sand / aggregate volume = Dry volume × their part ÷ (sum of parts)
Run the calculation to see each step with your own numbers.
A 10 ft × 10 ft slab, 4 in thick, 1:2:4 mix, 5% waste.
Wet = 33.3 ft³ ≈ 0.943 m³; dry = 0.943 × 1.54 = 1.453 m³
Cement = 1.453 × 1/7 = 0.208 m³ → 299 kg → 6.0 bags → order 7 bags (with 5%)
Sand = 0.415 m³ (≈14.7 ft³); aggregate = 0.830 m³ (≈29.3 ft³)
- A site (volume-batched) mix, not a designed ready-mix. Strengths shown next to each ratio are indicative, not guaranteed.
- 1.54 dry-volume factor accounts for the voids that fill when water is added and the mix is compacted.
- Cement bulk density 1,440 kg/m³ (loose) and a 50 kg bag. For an 94 lb (US) bag, divide the kg figure by 42.6 instead.
- Water is not calculated — follow the target water-cement ratio for your job.
- Why multiply by 1.54?
- Dry sand, aggregate and cement have air voids. When you add water and compact the mix, those voids fill, so you need about 54% more dry material than the finished wet volume.
- US 94 lb bags instead of 50 kg?
- A 94 lb bag is 42.6 kg. Take the cement weight in kg and divide by 42.6 for US bags.
- How many bags of cement for 1 cubic metre of concrete?
- About 6.3 bags of 50 kg at 1:2:4, 8.1 at 1:1½:3, 11.1 at 1:1:2 and 4.4 at 1:3:6, before waste. That uses the site-mix method's 1.54 dry-volume factor and a loose cement density of 1,440 kg/m³.
- Which mix ratio should I pick?
- 1:2:4 is the general-purpose option, 1:1½:3 and 1:1:2 are richer mixes, 1:3:6 is for mass concrete or blinding, and 1:4 or 1:5 are cement–sand mortars. The strengths shown next to each ratio are indicative only; a specified strength needs a designed mix.
- Does the calculator work for mortar as well as concrete?
- Yes. Choose the 1:4 or 1:5 cement–sand ratio; the aggregate result is then zero, and the cement and sand come from the same dry-volume method.
Dry-volume factor & method
Indian Standard IS 10262 / SP 23 site-mix method; the 1.54 factor is the standard bulking/voids allowance used in field mix design.
Cement bulk density
Loose Ordinary Portland Cement ≈ 1,440 kg/m³ (≈ 90 lb/ft³). Cement-industry data / IS 4031.
About the Cement Calculator
The Cement Calculator is for site-mixed (volume-batched) concrete or mortar rather than ready-mix. Give it the pour size and a mix ratio — cement to sand to aggregate — and it returns the number of cement bags plus the loose volumes of sand and aggregate to buy, using the standard 1.54 dry-volume factor. For ready-mix delivered by the yard use the Concrete Calculator; for the delivered price, the Concrete Cost Calculator.
What you enter
- Length
- Width
- Depth / thickness
- Mix ratio (cement : sand : aggregate)
- Waste allowance — Default 5%. Adjust to your own allowance — the exact figure is always shown too.
What you get back
- Cement (50 kg bags) — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Sand — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
- Coarse aggregate — shown as the exact figure and, separately, a recommended figure with your waste allowance added.
The formula, a worked example, the assumptions behind it and the sources are shown in full below the calculator.
Related calculators
- Concrete Calculator — How much concrete a rectangular slab or footing needs, in cubic yards or cubic metres.
- Concrete Cost Calculator — Estimated material cost of a concrete pour from its volume and a unit price.
- Mortar Calculator — Mortar quantity for a brick or block wall.
- Sand Calculator — Sand by volume and weight for bedding, fill or mixing.
- Plastering Calculator — Plaster (render) volume, plus cement bags and sand, for a wall or ceiling area from its thickness and mix ratio.
Related articles
- Concrete vs Cement: What's the Difference? — Cement is an ingredient; concrete is the finished product made from it. Mixing up the two terms is one of the most common mistakes in construction conversation.
- What Is Concrete Made Of? — Concrete is cement, water, fine aggregate and coarse aggregate — and the ratio between them determines almost everything about the finished material.
Part of the Concrete calculators.