Estimate how much wall putty you need from your wall area and your product's consumption rate, plus a wastage allowance.
Change this to match your putty product.
How to Use the Putty Calculator
Enter your total wall area.
Check your putty product's packaging for its consumption rate and enter it (default is 1.5 kg per 10 sq.ft, a common general estimate).
Click "Calculate" to see the required putty, before and after wastage.
From Kilograms to Bags: A Worked Example
With the default inputs, 1,200 sq.ft of wall at 1.5 kg per 10 sq.ft needs 180 kg of putty. Adding 10% wastage gives 180 × 1.10 = 198 kg.
Cement-based wall putty is commonly sold in 40 kg bags, with smaller packs also available. 198 ÷ 40 = 4.95, so you would buy 5 bags of 40 kg. Always round up to whole bags, and keep in mind that an opened bag left exposed to humid air can harden, so do not over-buy by a large margin either.
How the Consumption Rate Affects Your Order
The consumption rate is the biggest unknown in the calculation. For the same 1,200 sq.ft wall with 10% wastage:
Consumption (kg per 10 sq.ft)
Required Putty
With Wastage
40 kg bags
1.0
120 kg
132 kg
4
1.25
150 kg
165 kg
5
1.5
180 kg
198 kg
5
2.0
240 kg
264 kg
7
Manufacturers usually print coverage as an area per kilogram for a stated number of coats. To convert it for this tool, divide 10 by that coverage. For example, a coverage of 8 sq.ft per kg equals 10 ÷ 8 = 1.25 kg per 10 sq.ft. Make sure the number of coats in the printed figure matches what you plan to apply.
Practical Points Before You Start
Putty is a thin levelling layer, normally applied in two coats with sanding in between. It is not meant to fill deep cracks or correct badly uneven plaster, which should be repaired with plaster or a crack filler first.
Cure and dry new plaster fully, and fix any seepage or dampness before applying putty. Putty over a damp wall tends to bubble and flake within months, especially after the monsoon.
White cement-based putty is the common choice for interior and exterior walls. Ready-mixed acrylic putty is easier to apply but is generally intended for interiors. Follow the water ratio and working time printed on the pack.
Walls that are only being repainted and are in good condition often need only spot putty on damaged patches, so do not calculate for the full area unless every wall will be re-puttied.
Frequently Asked Questions
Required Putty (kg) = Wall Area × Consumption Rate ÷ 10. For example, 1,200 sq.ft at 1.5 kg per 10 sq.ft needs 1,200 × 1.5 ÷ 10 = 180 kg.
It depends on the putty brand, the number of coats, and how uneven the wall surface is. Always check your specific product's packaging for its recommended consumption rate.
The calculator has no separate coats field, so the rate you enter should already cover all the coats you plan. If your product states consumption for a single coat and you will apply two, double the rate before entering it.
Many interior jobs include the ceiling for a smooth finish. If yours does, add the ceiling area to the wall area before calculating. Ceilings are slower to work on, which matters more for labour than for the quantity of putty.
Usually yes. Putty leaves a porous surface, and a coat of primer over it seals it so the finish paint dries evenly. Use the Primer Calculator for that quantity, and follow the system recommended by your paint brand.