N

Runs in your browser · nothing is uploaded

Paint Calculator

Measure the room or each wall in this paint calculator, leave out doors and windows, and see how much paint and which tins you need — with primer worked out separately.

Surfaces to paint

m
m
m

Doors and windows to leave out

m
m
m
m
m²/L
%

Use the coverage printed on your tin — it changes with the product, color and how porous the surface is.

Tin sizes you can buy

L
USD
L
USD
L
USD

Paint needed

7.25 L

7.25L

of paint for the walls, including 10% extra

Net wall area
32.96 m²
36 − 3.04 openings
Walls
7.25 L
6.59 before extra
Tins to buy
1 × 2.5 L + 1 × 5 L
0.25 L spare
  1. walls = 2 × (4 + 3.5) × 2.4 = 36 m²
  2. paint = 32.96 m² × 2 coats ÷ 10 = 6.592 L
  3. × 1.1 extra = 7.251 L
  4. tins: fewest tins covering 7.25 L

An estimate. Textured, porous or dark surfaces, strong color changes and rollers versus sprayers all change how far paint goes.

How it's calculated

  • Wall area2 × (length + width) × height − doors and windows
  • Paintarea × coats ÷ coverage × (1 + extra %)

Worked example

100 m² of wall at 10 m² per liter: one coat is 100 ÷ 10 = 10 liters, two coats 20 liters. With 10% extra that's 22 liters — for example four 5 L tins and one 2.5 L tin.

Frequently asked questions

How much paint do I need for a room?+

Measure the wall area (room perimeter × wall height), subtract doors and windows, multiply by the number of coats and divide by the coverage on the tin. 100 m² at 10 m² per liter needs 10 liters for one coat and 20 liters for two, before any extra.

What coverage should I use?+

The figure printed on the tin. Many wall paints quote around 10–13 m² per liter or 350–400 ft² per US gallon, but rough, porous or dark surfaces and big color changes use more.

Is a gallon the same everywhere?+

No. A US gallon is 3.785 liters and an imperial (UK) gallon is 4.546 liters. Pick the one your tins and coverage figures use.

Do I need primer?+

Usually on new plaster, bare wood or metal, stains, and when covering a much darker color. Primer is a different product, so the calculator works it out separately.

Should I subtract doors and windows?+

Yes, for anything you won't paint. The calculator stops you if the openings come to more than the wall area rather than showing negative paint.

Which tins should I buy?+

Enter the sizes you can buy and, optionally, their prices. The calculator finds the cheapest whole-tin mix that covers what you need, or — without prices — the fewest tins that leave less than one small tin spare.

How much paint do I need for a 12 × 12 room?+

With 8 ft walls the four walls are 2 × (12 + 12) × 8 = 384 sq ft. Take off a 3 × 7 ft door and a 3 × 4 ft window and 351 sq ft is left. Two coats at 350 sq ft per US gallon need 2.01 gallons, or 2.21 with 10% extra: buy 2 gallon cans and 1 quart. The ceiling is extra.

How many coats of paint do I need?+

Two coats is the usual advice for walls, and the calculator starts at two. One coat can be enough when you repaint in the same or a similar color with a good-quality paint; a big color change, especially light over dark, may need a third or a primer first.

Can it work out paint for the ceiling?+

Yes. Tick the ceiling option and set its coats. In whole-room mode the ceiling area is the room's length × width; in individual-walls mode you enter it. It uses the same coverage as the walls, so if your ceiling paint quotes a different figure, run it separately.

What if my walls aren't a simple rectangle room?+

Switch to “Individual walls” and add each wall's width and height, with a count for identical walls. That handles open-plan spaces, alcoves, accent walls and single walls; gable ends and other triangles aren't covered.

Is anything I enter saved or sent?+

No. Everything is calculated in your browser and nothing is uploaded or stored.

More free Northlane tools