Mortar Joint Calculator

Inputs

Formula used

1) Net wall area: A_net = (L × H) − A_openings

2) Modular brick dimensions: L_m = L_b + J, H_m = H_b + J

3) Bricks per m² (one layer): N_m2 = 1 / (L_m × H_m)

4) Thickness layers: W = round(T / W_b)

5) Brick count with waste: N = ceil(A_net × N_m2 × W × (1 + w%))

6) Mortar volume with waste: V_mortar = max(0, A_net×T − N×V_brick) × (1 + w%)

This approach estimates mortar in joints by subtracting brick volume from wall volume.

How to use this calculator

1. Enter wall length, height, and thickness from drawings.
2. Add total door and window openings area if known.
3. Input the brick size you will purchase or use.
4. Set the joint thickness used by your masonry crew.
5. Choose a waste allowance for cutting and spillage.
6. Adjust bag yield if your mix differs from defaults.
7. Press Calculate to see bricks, mortar, and bag totals.
8. Download CSV or PDF for estimating and procurement.

Mortar joint estimating guide

1) Why mortar joint takeoff matters

Mortar quantity drives material cost, delivery timing, and crew productivity. Under-ordering causes stoppages and cold joints, while over-ordering increases waste and cleanup. This calculator converts wall dimensions, brick size, and joint thickness into a practical mortar volume and bag count for site planning.

2) Wall area and openings

Start with gross wall area (L × H) and subtract total openings area for doors and windows. A 6.0 m by 2.7 m wall gives 16.20 m² gross. If openings total 1.60 m², net area becomes 14.60 m². Net area is the key driver for both bricks and mortar.

3) Brick module concept

Brickwork is measured in modules: the brick plus one joint. If a brick is 190 mm long and the joint is 10 mm, the module length becomes 200 mm. The same applies vertically. Smaller joints raise bricks per square meter and reduce mortar volume; thicker joints do the opposite.

4) Thickness layers and wall volume

Wall thickness determines how many brick layers (wythes) are needed. The tool rounds thickness to a practical integer based on brick width. Wall volume is A_net × T. For 14.60 m² at 100 mm thickness, wall volume is about 1.46 m³ before waste.

5) Mortar as “wall volume minus brick volume”

Mortar fills the space not occupied by bricks. The calculator estimates brick count from modular dimensions, then multiplies by brick volume. Mortar volume is the remaining difference. This method is reliable for common bonds when input sizes match the actual products used on site.

6) Waste allowance and practical losses

Waste covers spillage, remixing, uneven joints, and cutting around corners and openings. Many crews use 5–10% for straightforward walls and 10–15% for complex detailing. Apply the same percentage to bricks and mortar to keep ordering conservative and realistic.

7) Bag yield and conversion to bags

Bag yield varies with mix design, sand moisture, and workability. If one bag yields 0.012 m³, then 0.24 m³ requires ceil(0.24 / 0.012) = 20 bags. Adjust yield to match your supplier’s data or site trials for improved accuracy.

8) Reading results like an estimator

Use net area and brick count to validate against drawings and bond patterns. Compare mortar volume to crew experience; large deviations often indicate unusual joint thickness, wrong brick dimensions, or incorrect openings. Export the CSV to keep a record for procurement and daily tracking.

FAQs

1) Does the calculator work for different brick sizes?

Yes. Enter the actual brick length, width, and height you will use. Modular dimensions are calculated automatically using the joint thickness, so the brick count and mortar volume adapt to the size provided.

2) What joint thickness should I enter?

Use the specified joint thickness from your project details or typical crew practice. Common values are 8–12 mm. Thicker joints increase mortar volume and may slightly reduce bricks per square meter.

3) How do I estimate openings area quickly?

Multiply each opening’s width by height, then add them together. For multiple identical windows, calculate one and multiply by the count. Enter the total as a single value to get net wall area.

4) Why does wall thickness change mortar volume so much?

Mortar volume is tied to wall volume. Doubling thickness nearly doubles wall volume and brick layers, so the remaining “void” volume also increases. Always confirm thickness in millimeters from drawings.

5) What waste percentage is reasonable?

Use 5–10% for straight walls with good access, and 10–15% for walls with many corners, returns, or small cuts. Poor mixing control and long carry distances also increase waste.

6) The bag yield is unknown. What should I do?

Start with the default yield and compare with a small on-site trial mix. Supplier datasheets may provide expected coverage. Adjust yield until calculated bags align with real consumption on similar work.

7) Is this suitable for blockwork or stone masonry?

It is optimized for brickwork. You can adapt it by entering block dimensions, but bonding and joint geometry differ. For stone or irregular units, a dedicated masonry mortar estimator is recommended.