Mortar Mix Calculator

Work out exactly how much cement, sand, and water you need. Choose a standard mix ratio or enter your own.

Volume of mortar needed

m³

Unit system

Mix type

You need

Cement: 443.52kg; 0.31 m³

Sand: 1,971.2kg; 1.23 m³

Water: 221.76litres

Using General purpose (1:4) ratio. Water calculated at 0.5 water-to-cement ratio.

How mortar mix ratios work

A mortar mix ratio describes the proportion of cement to sand by volume. A 1:4 ratio means one part cement to four parts sand — the standard general-purpose mix for bricklaying and blockwork in the UK.

Common mortar mix ratios

General purpose (1:4): Suitable for most bricklaying and blockwork above damp-proof course.
Strong (1:3): Used for load-bearing walls and areas subject to high stress.
Paving (1:3): For laying paving slabs and flagstones.
Render (1:5): A weaker mix for external wall rendering, allowing for expansion.

How this calculator works

Enter the volume of mortar you need. The calculator applies a bulking factor of 1.54 to account for the difference between wet (mixed) and dry material volumes, then splits the dry volume according to your chosen ratio. Cement density is taken as 1,440 kg/m³ and sand as 1,600 kg/m³. Water is calculated at a 0.5 water-to-cement ratio by weight.