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
Written by Jo Penhale, editor (a pen name).
Figures last checked 25 October 2026. Read how we calculate and our disclaimer. Found a mistake? Tell us.