Cement Mix Calculator — How Many Bags Do You Need?
Estimate 50 kg cement bags for your concrete mix two ways: from the area and thickness of a slab, screed or plaster — or directly from a concrete volume. Choose your mix ratio and get an instant answer.
Cement bags required
–
50 kg bags, rounded up
Wet volume
–
cubic metres
Dry material volume
–
wet volume × 1.54
Mix used
–
cement : sand : aggregate
How this cement calculator works
You buy cement in 50 kg bags but plan concrete and mortar in cubic metres — so something has to convert between the two, and that’s this calculator’s job. Give it a surface area plus thickness (for slabs, screeds and plaster) or a concrete volume directly. It converts your figure into dry material volume — the total space the loose materials occupy before mixing — takes cement’s share per your chosen mix, and divides by 0.0347 m³, the volume of one 50 kg bag.
The formula
- By area: wet volume = area (m²) × thickness (m)
- By volume: wet volume entered directly (cft ÷ 35.3147 = m³)
- Dry volume = wet volume × 1.54
- Cement bags = (dry volume × cement share) ÷ 0.0347, rounded up
For mortar-only mixes like 1:4, the calculator treats the mix as just cement + sand, and works out cement’s share of those two parts.
Worked example
Take a 100 sq ft floor screed, 2 inches thick, in 1:4 mortar. Area = 100 × 0.0929 = 9.29 m²; thickness = 2 × 0.0254 = 0.0508 m; wet volume = 0.47 m³; dry = 0.47 × 1.54 = 0.73 m³. Cement gets 1/5 of that: 0.145 m³ ÷ 0.0347 = 4.19 → round up to 5 bags.
Notes for Indian sites
Every cement bag in India is standardised at 50 kg, and one bag holds about 0.0347 m³. This calculator rounds the count up — but still keep one or two spare bags for touch-ups. Check the manufacturing date on every bag: cement older than 90 days can lose significant strength, and lumps inside the bag are a warning sign. Store bags off the ground on a dry platform, stacked no more than 10 high, and use the oldest stock first. If you’re plastering, here’s a handy cross-check: standard 12 mm plaster in 1:4 mortar needs roughly 2 bags per 100 sq ft.
Frequently asked questions
How many cement bags are in 1 cubic metre?
One cubic metre of dry cement weighs about 1,440 kg — roughly 28.8 bags of 50 kg cement. But you never buy 1 m³ of cement outright for a job. For concrete or mortar, the bag count depends on the mix ratio, and that’s what this calculator works out.
What is the volume of one 50 kg cement bag?
About 0.0347 cubic metres (34.7 litres), based on cement’s bulk density of 1,440 kg/m³. This calculator uses that figure to turn cement volume into bag counts.
How much cement is needed for 100 sq ft of plaster?
For 100 sq ft of plaster at 12 mm thickness in 1:4 mortar, you need roughly 0.17 m³ of dry mortar — about 1 bag of cement. But order 2 bags to be safe, since plastering wastes a lot of material.
How many cement bags per cubic metre of 1:2:4 concrete?
About 7 bags. 1 m³ of wet concrete × 1.54 dry factor gives 1.54 m³ of dry material. Cement’s 1/7 share is 0.22 m³, and 0.22 ÷ 0.0347 ≈ 6.34 — which rounds up to 7 bags of 50 kg cement.
Should I round cement bags up when ordering?
Yes. Running out mid-pour can ruin a slab or a wall section, and a spare bag keeps for months if stored dry — so there’s no downside. This calculator always rounds the bag count up to the next whole bag.
How do I calculate cement bags for a concrete mix?
Pick your mix ratio — for example 1:2:4 — then enter the concrete volume, or the slab area and thickness. This cement mix calculator converts it to dry material volume (wet volume × 1.54), takes cement’s share of the mix, and divides by 0.0347 cubic metres — the volume of one 50 kg bag. The result is rounded up to whole bags.