Mortar Mix

Free Mortar Mix calculator with clear step-by-step results.

About Mortar Mix

Mortar volume per square metre depends on the wall construction - a one-brick-thick wall needs more than twice the mortar of a single skin because of the collar joints. Wet volume is grossed up by a dry factor before being split by the mix ratio, and sand is converted to tonnes at typical bulk density.

Formulas

Mortar volume

Volume = wall area x mortar per m2 for the construction x (1 + waste)

Cement volume

Cement = wet volume x 1.33 / (1 + sand parts)

Worked example

With the default values below, Mortar Mix returns Wet mortar required of 0.5060. Change any input above and every figure here is recalculated in your browser.

Inputs used

Wall area to buildminimum 0.1 m2: 20 m2
Wall constructionone of Brick, single skin (102 mm), Brick, one brick thick (215 mm), Concrete block, 100 mm, Concrete block, 140 mm: Brick, single skin (102 mm)
Mortar mix (cement : sand)one of 1:3 - very strong, below ground, 1:4 - exposed or engineering brick, 1:5 - general purpose, 1:6 - internal or soft brick: 1:5 - general purpose
Waste allowanceaccepts 0–50 %: 15 %

Results

Wet mortar required: 0.5060 m3
Cement (25 kg bags): 6.46 bags
Building sand: 0.897 t
Mix proportions: 1 : 5

Step by step

1Values used
2Mortar volume
3Cement volume
4Wet mortar required= 0.5060 m3
5Cement (25 kg bags)= 6.46 bags
6Building sand= 0.897 t
7Mix proportions= 1 : 5

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Mortar specification for structural masonry, exposed situations and below-ground work is governed by design standards. Over-strong mortar can damage soft masonry - take advice on historic buildings.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Mortar specification for structural masonry, exposed situations and below-ground work is governed by design standards. Over-strong mortar can damage soft masonry - take advice on historic buildings.

Frequently Asked Questions

Why is the waste allowance so high?

Mortar is mixed in gauges, dropped from the trowel, and stiffens before it can all be used. Fifteen percent is realistic and twenty is not unusual on a windy day.

Should I add plasticiser or lime?

Lime improves workability and lets the mortar accommodate movement without cracking, which matters on soft historic brick. Modern plasticisers entrain air for similar workability but less flexibility.