Construction estimator
Brick / Block Calculator
Enter the wall size, the doors and windows to leave out, and the brick or block you are using to estimate how many to buy, plus the cement and sand for the mortar. Your entered values stay out of analytics.
Formula and assumptions
Wall volume = (length × height − openings) × thickness. Units = wall volume × (1 + unit wastage) ÷ volume of one unit with its joint on every side, rounded up. Mortar (wet) = (wall volume − units × unit volume) × (1 + mortar wastage); dry mortar = wet × 1.33. Cement and sand are shares of the dry mortar by the chosen ratio; cement bags = cement volume × 1,440 kg/m³ ÷ 50 kg, rounded up.
- Units are counted from the wall volume divided by the volume of one unit plus its mortar joint on every side. A modular brick is 500 per m³ of wall.
- Unit sizes are actual sizes without mortar. Hollow blocks are counted at their gross volume.
- Mortar is the wall volume minus the volume of the units. Dry mortar is 1.33 times the wet volume.
- Cement 1,440 kg/m³ and sand 1,600 kg/m³ bulk density; cement is bought in 50 kg bags.
- Unit wastage applies to the units and mortar wastage to the mortar. They are separate inputs, so each can be set for its own material.
- An estimate for buying materials. It does not cover plaster, reinforcement, lintels, bonding patterns, sand bulking or structural design.
- Quantities are shown to 2 decimal places. Units and cement bags to buy are rounded up to whole numbers; sand is not rounded to loads.
Formula version 1.0, last reviewed Reviewed by an external trade reviewer, 6 October 2026; released by the owner.
Frequently asked questions
What wall thickness should I enter?
The finished thickness of the wall in millimetres, for example 90 for a half-brick wall, 190 for a one-brick or one-block wall made of the sizes above, or 230 for a traditional nine-inch wall.
Are the sizes the actual size of the brick?
Yes. Enter the actual size without mortar. The calculator adds the joint on every side. A modular brick of 190 × 90 × 90 mm becomes 200 × 100 × 100 mm with a 10 mm joint.
My brick or block is not listed.
Choose Custom size and enter its length, width and height in millimetres. Preset dimensions are common examples. Confirm the actual brick or block dimensions supplied for your project.
How are hollow blocks counted?
At their full outer size, which is the gross unit volume. The voids inside a block are not taken out, so the estimate is based on the gross volume.
What about AAC blocks?
AAC blocks are not covered by this mortar model. They are laid with thin-bed adhesive, not a 10 mm cement-sand joint, so the mortar figures here do not apply to them. AAC will need its own calculation.
What does this not include?
Plaster, reinforcement, lintels and sills, bonding patterns, sand bulking, water, and any structural design. It is an estimate for buying materials.