Cement Calculator - Bags of Cement for Your Mix (UK)
Work out how many 25kg bags of cement you need for a given volume of mortar or concrete at a standard UK mix ratio.
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How to use this calculator
Enter the total volume of mortar or concrete you're mixing (in m³ - the mortar and concrete calculators give you this), pick the mix, and read off the cement bags.
How we calculate this
- Cement bags = volume × bags per m³ for the chosen mix.
- Indicative 25kg bags per m³: ~11 (mortar 1:4), ~9 (1:5), ~8 (1:6), ~12 (concrete 1:2:4).
- These allow for the dry materials yielding less wet volume - the classic reason naive volume maths comes up short.
Worked example
1 m³ of 1:4 mortar takes about 11 × 25kg bags of cement. A 0.5 m³ concrete pad at 1:2:4 takes about 6 bags.
UK notes & gotchas
- OPC (ordinary Portland cement) in 25kg bags is the standard. Keep it dry - damp cement is scrap.
- Stronger isn't always better: too much cement makes mortar brittle and prone to cracking.
- Pair cement figures with the matching sand/ballast - the mortar and concrete calculators handle that.
FAQ
How many bags of cement per m³ of concrete?
Around 12 × 25kg bags per m³ for a general 1:2:4 mix, plus sand and aggregate. Ready-mix is usually better value above ~1.5 m³.
How many bags of cement in a bulk bag of sand?
For a 1:4 mortar, roughly 5-6 × 25kg bags of cement to one ~0.5 m³ bulk bag of sand. Adjust for your mix.
Is a 25kg bag of cement the standard?
Yes - 25kg is the standard UK builder's merchant bag. Some places still stock larger bags, but 25kg is the norm.
Related calculators
mortar calculator · concrete slab calculator · sand calculator