Estimate the mortar volume, cement, and sand required for brick or block masonry. Enter your wall dimensions, block or brick size, mortar joint, mix ratio, and waste allowance to get a practical material estimate.
How the Mortar Calculator Works
The calculator first determines the wall area and estimates how many masonry units fit across that area. It then compares the combined volume of the units with the gross wall volume. The difference represents the approximate mortar volume within the masonry.
Wall Area = Wall Length × Wall Height
Wall Volume = Net Wall Area × Block Width
Unit Volume = Block Length × Block Height × Block Width
Unit Coverage = (Block Length + Joint) × (Block Height + Joint)
Estimated Units = Net Wall Area ÷ Unit Coverage
Mortar Volume ≈ Wall Volume − Masonry Unit Volume
The calculator applies a dry-volume factor of 1.33 to the wet mortar volume. This accounts for the reduction in volume that occurs when cement and sand are mixed and compacted. The result is then divided according to the selected cement-to-sand ratio.
Dry Material Volume = Wet Mortar Volume × 1.33
Cement Volume = Dry Material Volume ÷ (1 + Sand Ratio)
Sand Volume = Dry Material Volume − Cement Volume
Common Cement-to-Sand Mortar Ratios
| Mix ratio | Cement | Sand | Typical use |
|---|---|---|---|
| 1:3 | 1 part | 3 parts | Stronger or specified masonry work |
| 1:4 | 1 part | 4 parts | General masonry estimating |
| 1:5 | 1 part | 5 parts | General brick or block work where specified |
| 1:6 | 1 part | 6 parts | Less cement-rich mortar where specified |
Mortar specifications vary by project, masonry unit, exposure, structural requirements, and local building standards. Always use the specified mix where a project specification is available.
Worked Example
Suppose a wall is 6 m long and 2.7 m high. The wall uses 400 × 200 × 150 mm blocks with a 10 mm mortar joint. The mortar mix is 1:4 cement to sand, with a 10% waste allowance.
The gross wall area is:
6 × 2.7 = 16.2 m2
The calculator then estimates the block coverage, masonry unit volume, mortar volume, dry material volume, and the cement and sand portions of the selected 1:4 mix. The 10% allowance is added to the final mortar requirement for ordering and site losses.
The actual requirement varies with joint thickness and the dimensional accuracy of the blocks. A 5 mm change in joint thickness across a large wall can noticeably change the material estimate.
Common Mortar Estimating Mistakes
- Using the block dimensions without allowing for mortar joints.
- Forgetting to deduct large doors and windows from the wall area.
- Mixing up mortar volume with concrete volume.
- Using a cement-to-sand ratio different from the project specification.
- Ignoring waste, spillage, uneven joints, and material handling losses.
- Assuming every brick or block has identical dimensions.
- Ordering exact calculated quantities without allowing for supplier packaging or site conditions.