Wall putty consumption depends on the area and the build up thickness, as well as the product. The Whatson Wall Putty Calculator lets you enter a consumption figure in kg per m² per millimetre rather than assuming one universal bag coverage.
Use that basis only when it matches the information available for your product. A bag label giving total coverage for a complete application may need conversion before it fits this field.
Area first, thickness second
Enter the net surface to be treated and select square feet or square metres. Openings are not deducted inside this tool, so remove them before entering the area.
Thickness is total estimated build up in millimetres. The calculator has no separate coat count. If several applications produce a combined thickness, enter that combined thickness once.
Do not multiply the same thickness by coats again in the consumption field. Doing so would count the application twice.
A 1,000 sq ft example
Use area 1,000 sq ft, thickness 1 mm, assumed consumption 1.2 kg/m²/mm, bag size 20 kg and a 5% allowance.
The checked requirement is 117.06 kg. Rounding to whole bags gives six bags, containing 120 kg in total.
The difference between 117.06 and 120 kg is packaging, not another wastage percentage. The price calculation uses six bags because that is the proposed purchase.
When the wall is not uniformly ready
A rough wall with deep local hollows may need preparation or a different material rather than a thicker assumed putty coat everywhere. The calculator cannot judge substrate condition, moisture problems or a product’s permitted thickness.
Follow the intended product instructions and assess unusual areas separately. A small repaired patch and an entire newly plastered wall may have different consumption even when their visible finish looks similar.
Check the units on the supplier’s information
kg/m²/mm means each extra millimetre increases the assumed mass proportionally. A value given in m² per bag is the inverse type of quantity and must not be pasted into this consumption field unchanged.
The bag quote is PKR per bag. Primers, paint, labour, sanding and repairs are outside that cost. The Paint Calculator can estimate the subsequent paint separately using its coverage per litre per coat.
Keep the product and thickness assumption with your saved result. Those two details explain why another putty product may need a different order for the same 1,000 sq ft wall area.