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.
Open CalculatorRelated Calculators
FLFlorida Building Code
References & Sources
Standards Cited
- ASTM C270 — Standard Specification for Mortar for Unit Masonry
Defines mortar type designations (M, S, N, O) and mix proportions used in the calculator - TMS 602 — Specification for Masonry Structures
Guidance on mortar mix ratios and their applications for brickwork and CMU blockwork
Formulas Used
- Mortar volume:
baseVolume = wallArea x mortarRate x (mortarThickness / 10)
Source: TMS 602 — 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: ASTM C270 — 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: ASTM C270 / industry standard densities - Water requirement:
waterLitres = cementKg x 0.5
Source: TMS 602 — Approximate water-cement ratio of 0.5 by weight (typical mortar range 0.4-0.6)
Key Assumptions
- Cement density: 1506 kg/m3, sand density: 1602 kg/m3, hydrated lime density: 641 kg/m3 — ASTM C270
- Dry volume factor of 1.33 (more dry material needed than placed wet volume) — ASTM C270
- Typical mortar joint width: 10mm (3/8 in) — TMS 602
- Standard wastage allowance of 10% for mortar — Industry standard practice