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Masonry · units · sand · cement
How many bricks do I need?
The core one. 60 bricks or 10 blocks to the square metre, sand off the unit count, cement and lime off the sand by mix ratio — the same chain the old mortar sheet ran, with the below-DPC and above-DPC mixes it used.
1
Measure it
Every box has its own unit next to it.
Change the unit beside any box and the number converts. The (i) beside each question says what the box wants and where the figure usually comes from. Anything marked per cent is a percentage of the quantity above it.
2
Check the rates
Rates and assumptions used
These are the figures the calculator works to. Change any of them and the order list updates — your merchant’s pack sizes and your own waste allowances beat the defaults every time.
How this one works
Net area = length × height − openings
Units = net area × units per m² × (1 + waste %)
Sand = units laid × sand per unit — worked off the units actually laid, not the ones in the pack
Cement = sand ÷ sand parts × cement parts, same for lime
The figures the calculator works to. Every one can be changed in step 2, and your merchant’s pack sizes and your own waste allowances beat these defaults every time.
Rate
Default
Why
Bricks per m²
60 no.
Standard 65 mm brick on a 75 mm gauge, stretcher bond.
Sand per brick
1 kg
The old sheet’s figure. Roughly 10 mm joints.
Blocks per m²
10 no.
440 × 215 block.
Sand per block
1.8 kg
The old sheet’s figure.
Cement / lime bag
25 kg
Sand bulk bag
0.85 t
Bricks per pack
500 no.
Common merchant pack. Some are 400.
Blocks per pack
72 no.
Varies by manufacturer.
Wall ties
2.5 per m²
Standard spacing. More at reveals and movement joints.
A worked example
With the defaults the page opens on:
How long is it? 12 metres
How tall is it? 2.4 metres
Doors and windows to take off? 3.2 square metres
Brick or block? Facing brick — 60/m²
Which mortar mix? 3:1 — below DPC
Spare for breakages 5 per cent
Walling
Gross wall area: 28.8 m² — L × H
Openings deducted: 3.2 m²
Net wall area: 25.6 m²
Units per m²: 60 no.
Waste allowance: 5 %
Bricks to order: 1,613 no.— 1,536 laid, plus 5% spare
Packs: 4 packs — at 500 a pack
Mortar — mix 3:1
Building sand: 1.54 t— 1,536 bricks × 1 kg each
Sand bulk bags: 2 bags — 1.5 / 0.85 tonnes a bag
Cement: 21 bags— sand ÷ 3 = 512 kg, in 25 kg bags
Hydrated lime: none — use a plasticiser instead
Wall ties, if cavity: 64 no. — 2.5 to the square metre — see the cavity wall calc
Change any figure above and every line recalculates; the small print under each row is the sum that produced it.
Questions people ask
How many bricks are there in a square metre?
Sixty, for a standard 65 mm brick laid in stretcher bond on a 75 mm gauge, which is the figure this calculator uses. A 440 × 215 mm block is ten to the square metre. Both rates are in the rates panel and you can change them.
How much sand and cement do I need per 1,000 bricks?
This calculator works the sand off the bricks actually laid, at 1 kg of building sand per brick, then the cement off the sand by the mix ratio. At 3:1 that is about 1 tonne of sand and 14 bags of cement per 1,000 bricks; at 5:1:1 it is the same sand, about 8 bags of cement and 8 of lime. Change the mix and the figures follow.
Should I deduct doors and windows?
Yes - add up every opening in the run and put the total in "Doors and windows to take off". The old rule of thumb is not to bother deducting anything under about half a square metre, because the cutting round it uses what the opening saved.
Why is the pack count different from the brick count?
Merchants sell bricks by the pack, commonly 500 (some 400), so the order is rounded up to whole packs. The brick count is what you lay plus the spare; the pack count is what arrives.
Read before you order. These work out quantities, not structural design — spans, lintels, rebar and foundation depths need an engineer and Building Control sign-off. Waste allowances are defaults, not promises: awkward cuts, long runs and bad weather all eat more than 5%. Where a merchant sells whole packs, the figure is rounded up to whole packs.
