Cement Mortar Calculator

Work out how much cement and sand a mortar mix needs for brickwork or blockwork, based on the wall volume and your ratio.

Wall lengthft

Length of one wall section. Multiply by wall count for repeated walls.

Wall heightft

Height of the wall being covered, floor to ceiling.

Wall countpcs

How many walls have the same length and height.

Openings area (optional)m²

Total area of doors and windows to subtract from the wall area.

Wall thicknessft

Thickness of the finished wall, e.g. 0.24 m for a one-brick wall.

Wet mortar volume (optional)m³

Known wet mortar volume. Used instead of the wall dimensions when filled in.

Cement ratiopcs

Parts of cement in the mix, e.g. 1 for a 1:3 mix.

Sand ratiopcs

Parts of sand in the mix, e.g. 3 for a 1:3 mix.

Density (optional)kg

Bulk density of the mixed material. Defaults to a typical value if left empty.

Waste %%

Extra material for cuts, breakage and offcuts. 5–10 % is typical; use 0 for a theoretical value.

Units

Formula and method

Wall volume gives the wet mortar volume. A dry-to-wet factor converts this to dry material, which is then split between cement and sand according to the mix ratio. Density converts volume to mass.

How to measure the inputs

Measure the wall length and height and enter the wall thickness.
Deduct large openings to avoid over-ordering.
Confirm the mix ratio from the specification or your engineer.

Worked example

Wall length 16.4 ft; Wall height 9.84 ft; Wall count 1; Wall thickness 7.87 in; Cement ratio 1; Sand ratio 3; Density (optional) 3,968.32 lb; Waste 10 % → Total mortar mass: 26,125.44 lb

Practical tips

Mix only what you can use within about an hour of adding water.
Store cement off the floor and use older bags first.
Measure sand and cement by volume with the same container for consistency.

Assumptions

A standard dry-to-wet volume factor of about 1.33 is applied to account for bulking and voids.
The mix ratio is entered as parts by volume, for example 1:3 or 1:4.
Admixtures, lime and pigment are not included.

Frequently asked questions

What mix ratio should I use?

Common mixes are 1:3 for general brickwork, 1:4 for blockwork and 1:5 or weaker for non-structural bedding. Confirm the specification for your project.

Why is the dry volume larger than the wet volume?

Because sand bulks when damp and the voids between aggregate particles are filled by water. The dry factor of roughly 1.33 accounts for this.

How much water do I add?

Add water gradually to reach a workable consistency; a typical starting point is 0.5 litres per kg of cement, adjusted on site.

Does the mass include sand?

Yes. The mortar mass covers cement and sand together, which is what you will handle and buy.

Related calculators

Estimate only

Results are material quantity estimates only. They are not structural design, and they are not a substitute for local building codes, engineer approval or manufacturer instructions. Structural sizing — bar diameters, spacing, foundation depth and load-bearing capacity — must be confirmed by a qualified engineer for your site conditions.

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