Mortar Calculator (Cement & Sand)

How to use this calculator

Enter the wet mortar volume and the sand ratio (4 for 1:4). The dry volume, cement bags and sand volume are calculated.

Formulas

Dry volume = wet × 1.33
Cement = dry ÷ (1 + sand parts) Sand = cement × sand parts

Example — 1 m³ of 1:4 mortar

• Dry volume = 1.33 m³
• Cement = 1.33 ÷ 5 = 0.266 m³ = 7.7 bags of 50 kg
• Sand = 0.266 × 4 = 1.064 m³

Frequently asked questions

Why multiply by 1.33?

Dry materials shrink when water is added and voids fill, so about 33% more dry volume is needed than the final wet volume.

Which mix ratio should I use?

1:3 to 1:4 for strong work such as external plaster and load-bearing brickwork; 1:5 to 1:6 for internal walls. Follow your engineer's specification.

How much does a cement bag hold?

A 50 kg bag of cement occupies about 0.0347 m³ (cement bulk density about 1,440 kg/m³).

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