Cement Calculator
Estimate how much cement a pour needs from two inputs: the concrete volume in cubic metres and the cement content per cubic metre in kilograms. The second field opens at 350 kg/m³, a typical mid-range mix value, and the answer in kilograms converts straight to bag counts for ordering.
Your result will appear here.
Cement Calculator online
Work out how much cement a pour needs from the concrete volume and the mix's cement rate, and convert the answer into bags — for footing and slab planning before you order.
How it works
The relationship is linear: cement (kg) = concrete volume (m³) × cement rate (kg/m³). The rate is the mix’s cement content — how many kilograms of cement each cubic metre of fresh concrete contains — so changing the mix design changes the total without changing the volume. The 350 kg/m³ default suits a general structural mix; lean blinding mixes run near 200–250 kg/m³ while high-strength mixes reach 400–450 kg/m³.
Worked example
A 2 m³ footing pour at the default 350 kg/m³: cement = 2 × 350 = 700 kg. In 50 kg bags that is 700 / 50 = 14 bags; in 42.5 kg bags it is 700 / 42.5 = 16.5, so order 17 bags. A larger 4 m³ slab at the same rate needs 4 × 350 = 1400 kg, i.e. 28 bags of 50 kg. Always round bag counts up — half bags cannot be ordered.
Units
Volume is in cubic metres and the rate in kilograms per cubic metre, so the result is in kilograms. Divide by 1000 for tonnes (700 kg = 0.7 t). To get bags, divide by the local bag size (50 kg, 42.5 kg or 25 kg) and round up to whole bags.
Practical tips
- Confirm the rate from the approved mix design, not from memory. A 30 kg/m³ error on a 10 m³ pour swings the order by 300 kg — six 50 kg bags.
- Add 3–5% for spillage, formwork leakage and over-excavation, and compute that allowance on the cement total after the base multiplication.
- Store bags off damp ground under cover; one rainstorm can set the outer bags before the pour.
- This page estimates cement quantity for material planning. It does not design the mix — strength grade, water–cement ratio, admixtures and durability requirements should be settled with the supplier and reviewed by a qualified professional.
Edge cases and limitations
- Cement only. The result is the cement mass in the mix — not the sand, aggregate or water that complete it. A 350 kg/m³ rate says nothing about the other three ingredients; use the dedicated sand and gravel pages for those.
- Round bags up, then add a spare. Bag arithmetic always rounds up (16.5 bags means 17), and one extra bag covers the inevitable torn bag and spilled mix. Cement is cheap; a stopped pour is not.
- Rates belong to compacted volume. A cement rate is kilograms per cubic metre of placed, compacted concrete. If your mix design was specified per cubic metre of dry ingredients, convert first — dry volumes run roughly 1.5× the wet volume for nominal mixes, and confusing the two under-orders badly.
- Opened bags are perishable. Once opened, cement starts taking moisture from the air and loses strength within weeks. Prefer the bag size that matches your pour splits, and store bags off the ground, under cover, used oldest-first.
Privacy and browser processing
The calculation runs entirely in your browser — your figures are never uploaded.
Frequently asked questions
How much cement is in 2 m³ of concrete at 350 kg/m³?
2 × 350 = 700 kg, which is 14 bags of 50 kg or 17 bags of 42.5 kg after rounding up (700 / 42.5 = 16.5).
What cement rate should I enter?
Use the rate on your mix design. As a rough guide: about 200–250 kg/m³ for lean blinding, 300–350 kg/m³ for general slabs and footings, and 400–450 kg/m³ for high-strength or watertight mixes.
How do I convert the kilogram result to bags?
Divide by the bag size and round up. For 1400 kg with 50 kg bags: 1400 / 50 = 28 bags exactly. With 25 kg bags the same pour needs 1400 / 25 = 56 bags.
Does the calculator add waste?
No. It multiplies exact volume by the rate, so add your own allowance — typically 3–5% — and confirm the final volume against the concrete calculator before placing the cement order.