Mortar Calculator

Cement and sand for mortar, render or screed at 1:3 to 1:6: bags of cement, sand by weight and water, from a volume or the size of the job.

Mortar is cement and sand (and sometimes lime) mixed by volume, such as 1:4: one part cement to four parts sand. Dry materials shrink when water is added, so a cubic metre of mortar needs about 1.33 m³ of dry materials; at 1:4, that's 0.27 m³ of cement (about 383 kg, or 16 × 25 kg bags) and 1.06 m³ of sand. Enter the volume of mortar or the size of a screed or render, choose the mix, and this calculator gives the cement bags, sand, and water, with the working shown. To start from a wall, the brick and concrete block calculators work out the mortar volume for you.

Units
Bag sizes
Mixing
Enter
Area
ft
ft
in
Feet and inches work too: type 12'6 or 12.5.
%
Cement
5 bags

94 lb bag (1 ft³) · 418 lb

Sand
0.93 tons

0.69 yd³ · 1,860 lb

Water
25.07 gal

95 litres

How it was worked out
  1. Area: 10 ft × 10 ft = 100 ft²; × 2 in (0.167 ft) deep = 16.67 ft³
  2. 16.67 ft³ ÷ 27 = 0.62 yd³
  3. Plus 5% extra = 0.65 yd³ of mortar
  4. Dry materials bulk up when wet, so multiply by 1.33: 17.5 ft³ × 1.33 = 23.28 ft³ of dry materials
  5. 1 : 4 is 5 parts, so 1 part = 4.66 ft³
  6. Cement: 4.66 ft³ × 1,440 kg/m³ = 190 kg (418 lb) ÷ 94 lb = 5 bags
  7. Sand: 4 parts = 18.62 ft³
  8. Water at a water–cement ratio of 0.5: 95 litres (25.07 US gallons)

Assumes loose densities of 1,440 kg/m³ for cement, 1,600 for sand, 1,500 for aggregate and 1,650 for ballast, and a dry-volume factor of 1.54 for concrete and 1.33 for mortar. Damp sand bulks up, so measure by the bucket or shovel and adjust water as you go.

Common use cases

  • Sand and cement for bricklaying or blockwork mortar
  • A floor screed or render
  • Pointing and repointing
  • Checking what a 1:3 or 1:6 mix really uses

How to use

  1. Mortar / screed is already selected. Choose your units and bag sizes.
  2. Pick the mix ratio. Each option says what it's typically used for.
  3. Enter the size of the screed or render, or switch to Volume and type the mortar you need.
  4. Read the cement bags, sand and water.

FAQ

How much sand and cement do I need for mortar?

For 1 m³ of 1:4 mortar, about 383 kg of cement and 1.06 m³ of sand (about 1.7 tonnes). For 1:5, about 319 kg of cement and 1.11 m³ of sand. Damp sand bulks up, so measure by the bucket rather than by weight.

What do Type N, S and M mortar mean?

They're US mortar types by strength: Type N is general-purpose for above-grade walls, Type S is stronger and used below grade and for many structural uses, and Type M is the strongest. They're usually bought premixed or as masonry cement; this calculator works with cement-and-sand ratios.

What mix should I use?

General brick and blockwork is often laid with 1:4 to 1:5, internal walls with 1:6, and work below ground or strong renders with 1:3. Floor screeds are commonly 1:3 to 1:5. Follow your plans or the brick and block maker's guidance where it applies.

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