Use this calculator to find how many bricks you need for a wall and how much cement and sand goes into the mortar. It handles traditional red bricks, modular bricks and fly ash bricks, and lets you pick the mortar ratio.
How many bricks are in one cubic metre?
The trick is to count each brick together with its share of mortar. A traditional 230 × 110 × 75 mm brick with a 10 mm joint occupies 240 × 120 × 85 mm. Divide one cubic metre by that and you get about 408 bricks. A modular 190 × 90 × 90 mm brick with the same joint takes up 200 × 100 × 100 mm, which gives exactly 500 per cubic metre.
Mortar quantity
Whatever is left after the bricks is mortar. For traditional bricks it is roughly 22 to 25% of the wall volume. That is the wet volume, so it is multiplied by 1.33 to get the dry volume of cement and sand. The dry volume is then split according to the ratio. For 1:6 mortar, cement is one-seventh and sand six-sevenths.
Worked example
A wall 5 m long, 3 m high and 230 mm thick has a volume of 3.45 m³. With traditional bricks that needs about 1,410 bricks, or roughly 1,480 with 5% for breakage. The 1:6 mortar needs about 4 to 5 bags of cement and 0.9 m³ (around 31 cft) of sand.
Which mortar ratio to choose
- 1:4 for load-bearing walls in wet or exposed locations and for brick pillars.
- 1:5 for external walls of framed buildings.
- 1:6 for internal partition walls in 230 mm or 115 mm brickwork.
Soak red bricks for at least a few hours before laying. Dry bricks suck water out of the mortar and leave weak joints that crack later.
Frequently asked questions
Should I deduct doors and windows?
Yes. Work out the area of each opening, subtract the total from the wall area, then enter the adjusted length and height. The calculator does not deduct openings automatically.
How many bricks for a 4.5 inch wall?
A half-brick wall (about 115 mm) needs roughly 47 traditional bricks per square metre, or about 4.4 per square foot, before wastage.
Are fly ash bricks better?
Fly ash bricks are uniform in size, need less plaster and use industrial waste. Red clay bricks breathe better and are easier to find in rural areas. Both perform well when laid properly.