Brickwork and plaster
Brick and block calculator
This calculator works out how many bricks or blocks a wall needs, and how much cement and pit sand to buy for the mortar that holds them together. Enter the length and height of the wall, take off the doors and windows, pick the unit you are building with and whether the wall is one skin or two, and the quantities appear as you type.
What you need
This calculator works out the figures in your browser, which needs JavaScript switched on. The method below shows how to work it out by hand.
Estimates for planning and budgeting. Real quantities depend on the site and the workmanship, so check with your builder before you order.
It follows how walls are actually built in Zimbabwe: common bricks laid with a 10 mm mortar joint, pit sand for mortar rather than river sand, and cement in 50 kg bags. Single-skin walls (half a brick thick, about 110 mm) are usual for internal partitions; double-skin walls (one brick thick, about 230 mm) are usual for external and load-bearing walls. Brick sizes vary between suppliers and kilns, so if yours differ, choose a custom size and type in what you measured.
The figures are for planning and for checking a quote. A builder ordering for a whole house works from a bill of quantities, which accounts for every wall, opening and level at once.
How it is worked out
- Net wall area = length × height, less the doors and windows.
- Units per square metre of one skin = 1 ÷ ((unit length + joint) × (unit height + joint)). A common brick with a 10 mm joint gives about 52 per m².
- Mortar is the volume of the wall less the volume of the bricks in it, multiplied by 1.33 to allow for the sand and cement bulking down when water is added.
- That dry mortar volume is split by the mix ratio into cement (1 m³ weighs about 1,440 kg, so 28.8 bags of 50 kg) and pit sand (taken at 1.5 tonnes per m³).
What it assumes
- Stretcher bond; a header course uses about the same number of bricks per m² of wall.
- Mortar wastage is taken at the same percentage as the bricks.
- Brickforce, DPC and wall ties are not included.
Common questions
How many bricks are in a square metre of wall?
About 52 common bricks (222 × 106 × 73 mm) for a single-skin wall with 10 mm joints, and about 104 for a double-skin wall. Cement blocks of 390 × 190 mm work out at about 12.5 per m² of one skin.
Why pit sand and not river sand for mortar?
Pit sand has finer, more rounded grains and a little natural clay, which makes mortar and plaster smoother to work and better at holding water while it cures. River sand is coarser and cleaner, which is what concrete and screeds need for strength.
How many bags of cement for 1,000 bricks?
For a 1:4 mix, roughly 3.5 bags of cement and about 0.7 tonnes of pit sand per 1,000 common bricks with 10 mm joints. Thicker joints and uneven bricks use more; the calculator gives the figure for your wall and mix.
Want exact quantities for your plan?
A calculator works one wall or one slab at a time. A bill of quantities works from your actual drawings and counts everything, which is what builders price against and what stops you buying twice.