Mortar Calculator - Sand & Cement for Bricklaying (UK)
Tell it how many bricks you're laying and it works out the mortar volume, plus the bags of cement and bulk bags of soft sand you'll need for a standard bricklaying mix.
Interested? Then → Quotato for Builders · More advice on the Blog & Chips guides.
How to use this calculator
Enter the number of bricks for the job (the brick calculator gives you this). Pick your mix - 1:4 for exposed or below-DPC work, 1:5 for general use, 1:6 for sheltered internal work - and read off the cement and sand.
How we calculate this
- Mortar volume = bricks × 0.02 m³ per 60 bricks, plus 10% wastage (mortar gets dropped, boards get scraped).
- Cement bags per m³ of mortar: ~11 for a 1:4 mix, ~9 for 1:5, ~8 for 1:6 (25kg bags).
- Sand makes up the bulk of the volume - we take it as roughly 1 m³ of soft sand per m³ of mortar, then convert to ~0.5 m³ bulk bags.
Worked example
Laying 540 bricks in a 1:4 mix needs about 0.2 m³ of mortar. That's roughly 3 × 25kg bags of cement and 1 bulk bag of soft sand - give or take, depending on your joint thickness and how heavy-handed you are.
UK notes & gotchas
- Add a plasticiser (or a little lime) for workability - neat sand/cement is harsh to lay with.
- 1:4 below DPC and for exposed/coping work; 1:5-1:6 for general and sheltered work. Don't go too strong above weak bricks.
- Mortar figures are indicative - joint thickness and brick frog make a real difference.
FAQ
What mix should I use for bricklaying?
1:4 (cement:sand) for exposed and below-DPC work, 1:5 for general use, and 1:6 for sheltered internal work. A plasticiser improves workability.
How much mortar do I need per brick?
Roughly 0.02 m³ of mortar per 60 bricks as a working figure - about a third of a litre a brick - before wastage.
How many bricks does a bulk bag of sand lay?
Very roughly 800-1,000 bricks per bulk bag of soft sand in a typical mix, depending on joint size. This calculator gives a tighter figure for your job.