Paint Calculator

When this calculator helps

Guessing at the number of tins in a builders' merchant or DIY store is how a redecoration stalls — paint half on the wall and not enough left to finish. This calculator settles it: enter the room's length, width and height in metres, set how many doors and windows to subtract, choose your coats, and it returns the paintable wall area in square metres along with the litres of emulsion needed and how many 2.5 L or 5 L tins to buy.

It suits the decorating jobs common across the euro area — repainting an apartment before a new tenant moves in, refreshing a hallway in a shared building, or rolling a strong colour onto a single feature wall. Because you set the coats and the calculator applies a conservative coverage figure, the litres it gives are a realistic purchase target rather than the optimistic value printed on the tin.

How to read your result

Two numbers do the work. The paintable area in square metres is the wall left once doors and windows are removed — a 4 m by 5 m room at 2.4 m high gives around 40 m² of wall before openings. The litres figure is that area multiplied by your coats, divided by a coverage rate of roughly 11 m² per litre, which is a deliberately cautious reading of the 11–13 m² that European tins usually claim.

The calculator then rounds up to whole tins at the standard 2.5 L and 5 L sizes. Always round up: paint comes in fixed pack sizes, so a job needing 6 L means buying 7.5 L rather than stretching a single 5 L tin. The remainder is useful, not wasted — well sealed, emulsion keeps for about two years and covers later marks and touch-ups.

A worked example

Take a 4 m by 5 m living room with a 2.4 m ceiling. The four walls measure (4 + 5) × 2 × 2.4 = 43.2 m². Subtract one door at about 1.85 m² and two windows at roughly 1.4 m² each, leaving around 38.5 m² of paintable wall. For two coats that is 77 m² to cover, which at 11 m² per litre needs about 7 litres. The calculator rounds that up to one 5 L tin plus one 2.5 L tin — 7.5 L — with a little spare for touch-ups.

Common mistakes to avoid

Most paint shortfalls across the euro area come from a few estimating errors that are simple to avoid.

• Leaving out the second coat — a single coat seldom covers evenly, especially over a colour change, so set coats to two unless you are repainting like-for-like.
• Failing to deduct large openings — patio doors or floor-to-ceiling glazing remove far more wall than the standard averages, so adjust or add a tin.
• Skipping primer on bare or dark walls — fresh plaster and deep colours absorb paint, and without a primer you may need three finish coats instead of two.
• Taking the tin's coverage literally on porous or textured walls — fresh render, woodchip or chalky surfaces can use 15–20% more than a smooth primed wall.

Euro-area paint and product notes

Paint terminology and substrates vary across the euro area, even though coverage figures do not — what is Dispersionsfarbe in Germany is peinture acrylique in France, and primers range from Tiefgrund or Grundierung to a French sous-couche. Many continental homes have rendered or freshly plastered walls that drink more paint than a smooth primed surface, so for new render or porous plaster a thinned mist coat or a dedicated primer goes on first, and that layer counts when you are buying.

Tin sizes are standardised at 2.5 L and 5 L across most of the bloc, with 1 L and 10 L for trim and larger jobs, and the 5 L tins generally cost less per litre. Because EU VOC limits are strict, low-odour water-based emulsions dominate and behave consistently from one country to the next — so a coverage estimate made here holds whether you are buying in Berlin, Paris or Madrid, with only local product availability differing.