About This Calculator
This calculator estimates the quantities of cement, sand, and lime needed for mortar mixes used in bricklaying, blockwork, and rendering.
Mix Ratios
| Ratio | Strength | Best For |
|---|---|---|
| 1:3 | Very Strong | Foundations, heavy loads |
| 1:4 | Strong | Standard bricklaying |
| 1:5 | Medium | General purpose, blockwork |
| 1:6 | Standard | Internal blockwork |
| 1:1:6 | Flexible | Blockwork with lime |
Why Add Lime?
Lime makes mortar more workable (easier to spread), increases flexibility, and improves water retention. It also helps prevent cracking as the mortar dries.
Mixing Tips
- • Measure materials by volume using a bucket or gauge box
- • Mix dry ingredients first, then add water gradually
- • Mix for at least 3 minutes for consistency
- • Use within 2 hours of mixing (less in hot weather)
- • Add 10% wastage for general work
Water Content
Use approximately 0.2-0.25 litres of water per kg of cement. Too much water weakens the mortar; too little makes it unworkable. The mix should hold its shape when formed into a ball.
Ready to Calculate?
Enter your wall area and mix ratio to get material quantities.
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UKUK Building Regulations
References & Sources
Standards Cited
- BS EN 998-2 — Specification for mortar for masonry — Masonry mortar
Defines mortar classifications, mix designations, and performance requirements used in ratio selection - BS 5628-3 — Code of practice for the use of masonry — Materials and components, design and workmanship
Guidance on mortar mix ratios (1:3, 1:4, 1:5, 1:6, 1:1:6) and their applications
Formulas Used
- Mortar volume:
baseVolume = wallArea x mortarRate x (mortarThickness / 10)
Source: BS 5628-3 — Empirical rate: brickwork 0.025 m3/m2, blockwork 0.015 m3/m2 at 10mm joints, scaled linearly with joint thickness - Dry volume from wet volume:
dryVolume = wetVolume x 1.33
Source: BS EN 998-2 — More dry material is needed than wet volume because loose dry materials compact when mixed - Material weights:
weight = volume x density (cement: 1440 kg/m3, sand: 1600 kg/m3, lime: 640 kg/m3)
Source: BS EN 998-2 / industry standard densities - Water requirement:
waterLitres = cementKg x 0.5
Source: BS 5628-3 — Approximate water-cement ratio of 0.5 by weight (typical mortar range 0.4-0.6)
Key Assumptions
- Cement density: 1440 kg/m3, sand density: 1600 kg/m3, hydrated lime density: 640 kg/m3 — BS EN 998-2
- Dry volume factor of 1.33 (more dry material needed than placed wet volume, as loose dry materials compact when mixed) — BS EN 998-2
- Typical mortar joint width: 10mm — BS 5628-3
- Standard wastage allowance of 10% for mortar — Industry standard practice