How much wastage should I allow?

Wastage covers cuts, breakages and the offcut at the end of every run. Ordering the exact computed quantity reliably means a second trip.

Construction & HomefinishingIndia only

Primer and Putty Calculator

Primer and wall putty quantity from area and coverage. Putty is applied in two thin coats and covers far less per kilogram than primer does per litre.

Also called: wall putty calculator, primer quantity.

Primer or putty

1.83

1.83 kg or litres for 20 m² over 1 coat(s), including 10% wastage.

Area after deductions (m²)

Area across all coats (m²)

Before wastage

1.67

Area one unit covers (m²)

How this is calculated

Method and background

How this is calculated

Area times coats divided by coverage. Putty typically covers 10 to 15 square metres per kilogram over two coats; primer covers 10 to 14 per litre. Both go further on a sealed surface than on fresh plaster.

quantity = area * coats / coverage per unit, plus wastage

A: Net area (m2)
c: Coats (count)
r: Coverage per unit (m2)
s: Wastage (decimal)

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

two coats of putty

Length (m): 12
Width or height (m): 3
Or enter the area directly (m²): 0
Openings to deduct (m²): 0
Coverage per unit (m²): 12
Coats or layers: 2
Wastage: 10%

Primer or putty6.6

36 m² over two coats at 12 m² per unit

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one coat halves it

Length (m): 12
Width or height (m): 3
Or enter the area directly (m²): 0
Openings to deduct (m²): 0
Coverage per unit (m²): 12
Coats or layers: 1
Wastage: 10%

Primer or putty3.3

boundary

Open this example

Method and limits

What it assumes

Coverage as stated by the manufacturer for a prepared surface.

What it deliberately does not model

Fresh plaster absorbs heavily and can take half again as much on the first coat.

Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator

Frequently asked questions

How much wastage should I allow?: Wastage covers cuts, breakages and the offcut at the end of every run. Ordering the exact computed quantity reliably means a second trip.