How to price a painting job (square metres and coats)

The basis is area, not rooms. You find the wall area by multiplying the room's perimeter by the ceiling height and subtracting openings. A room of 4 by 5 metres has a perimeter of 18 metres. With a ceiling height of 2.5 metres, that gives 45 m² of gross wall surface.

From there you subtract doors and windows. A standard door takes up about 1.8 m², a window typically 1.2 to 2 m². With one door and two windows you end up at roughly 40 m² of net wall surface. The ceiling is calculated separately as length times width, so 4 by 5 = 20 m².

• Walls: perimeter x height minus openings (doors, windows)
• Ceiling: length x width
• Woodwork: measure panels, frames and trim separately, they have different consumption and different hours
• Calculate each surface on its own so you can apply different treatment

The number of coats drives both paint consumption and hours, and this is where most quotes go wrong. On a previously painted, intact wall two coats will often do. On a new substrate, filled repairs or strong colour changes you should count on a primer plus two coats, sometimes three.

Ceiling, wall and woodwork are not treated the same. Woodwork usually needs a primer and two finishing coats to cover and look clean, while a ceiling in the same colour can be done in two. Always write the number of coats per surface so the customer can see it, and so your own back-calculation adds up.

Preparation is real work and real hours, and it should stand on its own, not be hidden in a rounded square metre price. Break it down so both you and the customer can see what is included:

• Masking of floors, furniture and fixtures
• Filling of holes, cracks and screw holes
• Sanding and cleaning before painting
• Cleaning and spot-priming of stains

On a worn substrate the preparation alone can take more hours than the painting itself. If you do not put it in, you pay for it yourself.

You do not guess paint consumption. The manufacturer's data sheet states the coverage, typically as m² per litre or litres per m² per coat. A wall paint with a coverage of 7 m² per litre uses about 0.14 litres per m² per coat.

The calculation for 40 m² of wall in two coats: 40 x 2 = 80 treatment m², divided by 7 m² per litre gives about 11.4 litres. Add a little for waste and round up to a whole tin size. On an absorbent, new substrate the coverage drops on the first coat, so follow the data sheet's figures for priming separately instead of using the same coverage all the way through.

Hours follow surface, coat and access. A smooth wall with a roller goes fast, while panels, trim and frames done with a brush take significantly longer per m². Calculate hours per coat, not per room, so an extra coat also costs an extra chunk of work in the calculation.

Drying time between coats governs the schedule, not the price directly, but it determines how many coats you can manage in a day. If you can only apply two coats a day because of drying time, the schedule and any extra travel must reflect it. Be honest about it in the quote so the customer does not expect three-coat woodwork finished the same afternoon.

New build and maintenance are two different calculations. On a new substrate you pay for primer, higher consumption on the first coat and usually an extra coat to get even coverage. On maintenance of an intact, previously painted surface you often get away with two coats and minimal preparation, but this is exactly where you should inspect the substrate, because hidden repairs move the hours significantly.

Calco calculates it for you: you enter the surfaces' square metres and how many coats each surface needs, and Calco converts it to litres of paint using the data sheet's coverage and adds hours based on the number of coats and surface type. Then preparation, priming and finishing stand as separate line items, and you send a quote that matches what you actually do. See the painter template at /tilbud-maler.