Mortar is the material between the bricks. Estimating it as a fixed percentage of every wall can hide the effect of brick size and joint thickness. The Whatson Mortar Calculator instead approximates the wall’s brick solids and subtracts them from the net masonry volume.
The remaining wet joint volume is converted to loose cement and sand using the entered dry factor and mix ratio. It is an estimating model, rather than a detailed bond calculation.
Keep the wall and opening units separate
Wall length and height follow the chosen measurement unit. Wall thickness and brick dimensions are entered in inches. The deduction field is always square feet.
A 3 × 7 ft doorway is a 21 sq ft deduction. Enter 21 once. The deduction is an area, not a volume and not a count of openings.
For a wall with several openings, add their areas before filling that field. The separate Door & Window Area Calculator can help record the measurements, although its total may include openings outside this particular wall.
A checked brickwork estimate
Use a 20 × 10 ft wall, 9 inch thickness and a 21 sq ft deduction. Set the brick to 9 × 4.5 × 3 inches, the joint to 0.375 inch, sand parts to 6, dry factor to 1.33, bag size to 50 kg and cement density to 1,440 kg/m³. Add a 5% allowance.
The calculator returns about 0.81 m³ of measured joint mortar, 231.86 kg of cement, 5 whole bags and 34.12 cft of loose sand.
The 0.81 m³ figure comes before allowance and dry conversion. Comparing it directly with the loose sand volume would mix different stages of the calculation.
Where a masonry estimate becomes less exact
Corners, cut bricks, uneven beds and actual bonding can shift the quantity. Mortar dropped during work may also differ from the chosen allowance. Measure actual bricks and avoid assuming every delivery has exactly the same dimensions.
This tool does not choose a mortar specification for you. Its cement share is one part and the sand parts are editable; use the required specification rather than treating the default six sand parts as a universal instruction.
Check the order against the rest of the job
The cost fields are PKR per cement bag and PKR per cft of sand. Brick purchases and labour are separate. If you already included mortar in a contractor’s inclusive quote, adding this material estimate again could duplicate that cost.
Keep one set of wall measurements for the brick and mortar estimates. A mismatch in deductions can otherwise make two reasonable results disagree.