Cement Quantity Calculator
Get total cement, bag count and the cement/fly-ash split for a given volume and grade.
Inputs
Result
Formula
| Volume with waste | V_total = V × (1 + waste %) |
| Cement per m³ | mc = reference × (1 − replacement %) |
| Total cement | M = mc × V_total |
| Bags | N = ceil(M ÷ 50) |
| Fly ash | mf = reference × replacement % × 1.15 |
10 m³ of C30 with 3% waste: 360 kg/m³, so 3600 kg total — 3.60 t or 72 bags of 50 kg. At 20% fly ash, cement drops to 288 kg/m³ (about 2966 kg total) plus roughly 828 kg of fly ash.
FAQ
How much is a bag of cement?
The standard bag in China is 50 kg, marked 50±1 kg. Some small plants sell 40 kg or 45 kg bags that look cheaper per bag but cost more per tonne. Always convert using the actual pack weight rather than counting bags.
Why is fly ash used in excess of the replacement level?
Fly ash contributes little early strength, so equal-mass replacement loses strength. Practice is to replace 20% of cement but add 1.15-1.3 times that mass. The benefits are lower heat of hydration, better workability and lower cost; the price is slower early strength and poorer carbonation resistance, so use it cautiously in winter and in precast work.
Can I cost a job from the cement quantity alone?
It gives material cost only, not total cost. Concrete also carries aggregate, admixture, batching, haulage, pumping, testing and waste. For site-mixed concrete use these figures; when buying ready-mix, price by volume and use the cement figure only to sanity-check the supplier's mix.
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.