Brick calculator with mortar, sand and cement

The brick count, worked through

Each brick takes up its own size plus one mortar joint. A standard UK brick is 215mm long and 65mm high, and with a 10mm joint it fills a space of 225mm by 75mm on the face of the wall. That is 0.016875m², so one square metre holds 59.26 bricks in a half-brick wall. The calculator multiplies the net wall area by that figure, doubles it for a one-brick wall, adds your wastage and rounds up.

The method matches the Brick Development Association's own brick calculator, which gives 60 bricks for 1m² of single skin, 120 for double skin, and 593 for 10m². Wienerberger confirms 215 × 102.5 × 65mm with a nominal 10mm joint as the standard UK size.

Mortar comes from the number of bricks laid, not the area, using a manufacturer's yield figure. The mortar section below shows where that number comes from.

Worked example: the outer leaf of a single-storey extension wall, 5.0m long and 2.4m high, with one window 1.2m wide and 1.0m high. Half-brick, standard bricks, 5% wastage and a 1:4 mortar.

• Gross area: 5.0 × 2.4 = 12.0m².
• Take off the window: 1.2 × 1.0 = 1.2m². Net area 10.8m².
• Bricks laid: 10.8 ÷ (0.225 × 0.075) = 640 bricks.
• Plus 5% wastage: 640 × 1.05 = 672 bricks to order.
• Mortar: 640 ÷ 1,800 bricks per m³ = 0.36m³.
• Dry sand and cement: 0.356 × 1,820kg = 647kg. At 1:4, one part in five is cement: 129kg, so 6 bags of 25kg. The other four parts are sand: 0.52 tonnes.
• At 1:5 the same wall needs 5 bags of cement and 0.54 tonnes of sand.

How many bricks per square metre

For standard 65mm bricks, allow 60 per m² of half-brick wall and 120 per m² of one-brick wall. The exact figure is 59.26, so on a big wall the rounded 60 adds about 1% before you have counted any wastage.

Half-brick (single skin) is one brick thick, 102.5mm, with every brick laid lengthways. It is the brick outer leaf of a cavity wall, a garage or a low garden wall. One-brick (double skin) is 215mm thick, two bricks deep, and needs twice as many. For a cavity wall with a block inner leaf, count the brick leaf as half-brick and the blocks separately.

Older houses often have imperial bricks, which are taller. If you are matching existing brickwork, measure a brick and pick the height in the calculator. The BDA's figures per m² for each height are below.

How much mortar, sand and cement

Allow about 0.56m³ of mortar per 1,000 bricks in a half-brick wall, and about 0.71m³ per 1,000 in a one-brick wall. Those figures come from Tarmac's data sheet for Blue Circle Quality Assured Mortar, which says 1m³ lays 1,800 to 2,000 bricks in a 102.5mm wall and 1,400 to 1,600 in a 215mm wall, with 10mm joints and the frog up. The calculator uses the lower brick count of each range, so it errs towards more mortar.

A second maker agrees. Hanson's sand cement mortar data sheet gives a yield of 0.011m³ for a MaxiPack, enough to lay about 22 standard bricks. That works out at 0.5m³ per 1,000.

To turn mortar into materials, the calculator uses 1,820kg of dry sand and cement per m³ of mortar, from Hanson's 20kg MaxiPack making 0.011m³. Tarmac's Blue Circle bag yields more, 0.0135m³ per 20kg, which is about 1,480kg per m³. The calculator takes Hanson's figure, so its sand and cement are at the generous end. It then splits the weight by your mix. At 1:4, cement is one part in five by weight and sand the other four. At 1:5, cement is one part in six.

Per 1,000 bricks in a half-brick wall, before any extra, that gives these figures.

Which mortar mix: 1:4 or 1:5

Use what the job specifies. Where nothing is specified, 1:4 is the stronger general mix and 1:5 the softer one. The Mineral Products Association's table of prescribed mortars puts cement and sand at 1:3 to 4 in class M6 and 1:5 to 6 in class M4, by volume. It lists M6 as suitable for severe exposure and M4 for moderate.

Some calculators online say 1:6 is an M2 mix. In the MPA table, 1:6 is still M4, and M2 is 1:7 to 8. That matters if you are matching a specification.

The MPA proportions are by volume, which is how a mix is gauged on site: buckets or shovels of cement to sand. The calculator splits the dry weight instead, because a weight is what you buy. A bucket of cement and a bucket of damp sand do not weigh the same, so treat the split as a close guide, and gauge every mix the same way so the colour and strength stay even.

Two practical points. A softer mortar suits softer bricks, and the MPA's guide to specifying an appropriate mortar ties the class to the exposure of the wall. And the MPA notes that its sand range depends on the sand: use the lower figure with sand that has more fines in it.

Openings, cuts and wastage

Measure every window and door opening and take it off. The calculator subtracts width × height for each one. A door is a big hole: a 0.9m by 2.1m opening is 1.89m², or about 112 bricks in a half-brick wall.

The default wastage is 5%, and you can change it. Raise it if the wall has lots of cuts, piers or returns, or if the bricks are soft handmade ones that chip in the pallet. Lower it for a plain run where whole bricks go in almost every time.

Bricks are sold in packs, and the pack size varies by brick and maker, so round your order up to whole packs with the merchant. Order them in one go where you can, or ask the merchant whether a later delivery will match.

• What the calculator does not count: blocks for an inner leaf, wall ties, lintels, cavity trays, damp proof course, insulation, coping or brick-on-edge tops, and foundations.
• Foundations: the concrete calculator works out a strip footing.
• It does not price anything. Brick prices vary far more than sand and cement, so ask the merchant.

Before you order the bricks

Check the brick size before trusting any brick count, including this one. Most new bricks are 215 × 102.5 × 65mm, but a 73mm imperial brick cuts the count by about 9%. Measure one and pick its height.

Measure the wall to the outside of the brickwork, not to the edge of the foundations, and measure the height from the top of the footing. For a stepped or sloping garden wall, split it into rectangles and add them.

Pricing it for a customer? Put the bricks, mortar materials and labour on the quote template with a valid-until date. Brick prices can move between quoting and ordering.

Common questions