Mortar Calculator
Estimate mortar for brickwork
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Result
Ready to calculate...
What this calculator does
Estimates mortar volume and 25 kg bags for laying a known number of bricks, from the joint thickness.
How to use it
- Enter the number of bricks and their size.
- Enter the mortar joint thickness.
- Set waste and read the volume and bags.
Formula
brickLengthInMetres = Brick Length/100, brickHeightInMetres = Brick Height/100, brickDepthInMetres = Brick Depth/100, jointInMetres = Mortar Thickness/1000 mortarPerBrick = (brickLengthInMetres+jointInMetres) × (brickHeightInMetres+jointInMetres) × brickDepthInMetres − brickLengthInMetres × brickHeightInMetres × brickDepthInMetres Material volume m³ = mortarPerBrick × Brick Count × (1 + Waste Margin (%) / 100) Mortar bags = roundUp( Material volume / 0.015 )
Formulas are shown in metric units, exactly as the calculator computes them. Imperial entries are converted to metric first. Waste is applied as a multiplier (1 + waste/100).
Areas are in m² and volumes in m³. Centimeters are divided by 100 to give meters. Millimeters are divided by 1,000 to give meters. RoundUp means the next whole piece or bag.
Variables
| Variable | Unit | Default |
|---|---|---|
| Brick Count | - | 1,000 |
| Brick Length | cm | 21.5 |
| Brick Height | cm | 6.5 |
| Brick Depth | cm | 10 |
| Mortar Thickness | mm | 10 |
| Waste Margin (%) | % | 10 |
Worked example
Using the default values of this calculator (Brick Count = 1,000, Brick Length = 21.5 cm, Brick Height = 6.5 cm, Brick Depth = 10 cm, Mortar Thickness = 10 mm, Waste Margin (%) = 10 %), the calculator returns:
brickLengthInMetres = 21.5/100, brickHeightInMetres = 6.5/100, brickDepthInMetres = 10/100, jointInMetres = 10/1000 mortarPerBrick = (brickLengthInMetres+jointInMetres) × (brickHeightInMetres+jointInMetres) × brickDepthInMetres − brickLengthInMetres × brickHeightInMetres × brickDepthInMetres Material volume m³ = mortarPerBrick × 1000 × (1 + 10 / 100) Mortar bags = roundUp( Material volume / 0.015 )
- Mortar bags: 22 bags (25kg)
- Material volume: 0.319 m³
Assumptions and limitations
- Assumes 0.015 m³ per bag; products differ, so check yield.
- Only the joint volume added to each brick is counted.
Waste, rounding and buying
Round up bags. Mortar sets and cannot be stored mixed, so mix in batches.
Frequently asked questions
- Where do I get the brick count?
- Use the Brick calculator and enter that count here.
- Why is the result lower than expected?
- Only joints are counted, assumed 10 mm by default.