How this is worked out
Wall area is length × height, less the doors and windows. For bricks we use 60 per m² per skin, from Wienerberger’s table for a 215 × 102.5 × 65mm brick with a 10mm joint. For blocks we use 10 per m²: a 440 × 215mm block plus 10mm joints covers 0.101 m².
Mortar is a rough guide only, at about 0.02 m³ per m² of half-brick wall and 0.011 m³ per m² of blockwork. We turn that into bulk bags of building sand at about 850kg a bag. Frogged bricks, wide joints and messy work all use more, so treat the sand figure as a minimum.
Worked example
A garden wall 5m long and 1m high, one skin thick: 5 m² × 60 = 300 bricks, or 315 with 5% for waste. Mortar comes to about 0.1 m³, so one bulk bag of building sand plus cement covers it with plenty to spare.
What this doesn’t cover
Foundations, copings, wall ties and damp-proof course are separate. A garden wall over about 1m, or any retaining wall holding back soil, needs proper design. Walls next to a road and boundary walls over 2m in England need planning permission.
Questions people ask
How many bricks are in a square metre?
Wienerberger gives 60 standard UK bricks (215 × 102.5 × 65mm) per m² with a 10mm joint. That’s for one skin, the half-brick wall you see on most garden walls and house fronts.
How many bricks do I need for a double skin wall?
Twice as many: about 120 per m² for a one-brick (215mm) wall. Set the skins to 2 in the calculator.
How many concrete blocks per m²?
About 10 standard 440 × 215mm blocks per m² with 10mm joints. The block thickness (100mm, 140mm and so on) doesn’t change the count.
How much waste should I allow for bricks?
Five per cent is common for straight walls. Allow more if there are lots of cuts, piers or a decorative bond, and order all your bricks at once so the colour batch matches.
Sources
Trade review pending. A named tradesperson will check this calculator, and their name and qualifications will appear here.
Figures last checked 25 October 2026. Read how we calculate and our disclaimer. Found a mistake? Tell us.