# Cement Quantity Calculator

Get total cement, bag count and the cement/fly-ash split for a given volume and grade.

- Page: https://jianzhujisuan.com/en/cement-quantity
- Category: Concrete (https://jianzhujisuan.com/en/c/concrete)
- Chinese version: https://jianzhujisuan.com/zh/cement-quantity.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Concrete volume 10 m³, Concrete grade C30, Fly ash replacement 0%, Waste allowance 3%): **Total cement 3708 kg**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Concrete volume | number | 10 | m³ |  |
| Concrete grade | select | C30 | — |  |
| Fly ash replacement | number | 0 | % | Typically 15-25%; up to 30% for mass concrete |
| Waste allowance | number | 3 | % |  |

## 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

## Worked example

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.

## Questions

### 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.

## Related tools

- [Concrete Volume Calculator](https://jianzhujisuan.com/en/concrete-volume): Enter length, width and thickness to get the concrete volume you need and how many truck loads that is.
- [Formwork Area Calculator](https://jianzhujisuan.com/en/formwork-area): Pick a member type, enter section and length, and get the formwork contact area plus sheet and batten estimates.
- [Concrete Mix Design Calculator](https://jianzhujisuan.com/en/concrete-mix-ratio): Work out cement, sand, gravel and water per cubic metre from the target grade and water-cement ratio.
- [Concrete Pour Sequencing Calculator](https://jianzhujisuan.com/en/concrete-pour-plan): Divide a slab into strips and get the volume, truck count and duration for each pour.
- [Concrete Strength Converter](https://jianzhujisuan.com/en/concrete-strength-convert): Convert between grade, MPa, psi and kgf/cm², with cube-to-cylinder correction.
- [Concrete Curing and Maturity Calculator](https://jianzhujisuan.com/en/concrete-curing): Turn curing temperature into maturity and equivalent age, and check the code minimum.

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