Spike's Calculators

Interior Finishing

Wall Paint Calculator

Spike's Calculators

How much paint will it take to paint a wall?

In the US, paint comes in 5-gallon buckets, one-gallon cans and one-quart cans.
They use the exact sizes in Canada, except it shows the metric equivalent for the US gallons and quarts on the label. But when you go to the store in Canada, you can still ask for a gallon of paint.

5 gallon bucket =  18.9 litres
1 gallon can    =  3.78 litres
1 quart can     =  946  millilitres

The manufacturer will indicate the square footage that the can of paint will cover, and depending on the brand and type of paint, you can get anywhere from 250 to 400 square feet of coverage per gallon of paint.
The actual coverage will depend on the texture of the wall and the colour you are using to paint. A smooth wall will take less paint than a rough-textured wall.

Covering a lighter colour wall with darker paint will take less paint than painting a lighter colour over a dark colour wall. The way you apply the paint, the equipment you use to paint with, and how much paint ends up on you or the floor versus the wall will impact how much paint you need.

Take the indicated square footage of coverage with a grain of salt and make sure you have enough paint on-site to complete the job. If the calculated result of the paint = 0.75 gallons, you could buy 3 quarts, but these 3 quarts most likely will cost you more than if you purchased the same paint in the gallon size.
Keep in mind that it is always good to have a bit of paint leftover for touch-ups at a later time.

Paint Calculator

Length of Wall: ft
Height of Wall: ft
Window/Door Openings: ft ²
Area covered by one
gallon of paint:
ft ²
How many coats: #


Total wall area: ft ²
Wall area minus openings: ft ²
Paint needed per coat: gallon
Paint needed in gallons: gallon
Paint needed in liters : liters


  1. enter the length of the wall in feet
  2. the height of the wall in feet
  3. the areas that do not need paint in square feet
  4. manufactures suggested coverage of one gallon of paint
  5. the number of coats you are applying


  1. the area of the wall in square feet
  2. the total area that needs painting
  3. the estimated amount of paint it takes per coat
  4. the amount of paint you need in the number of gallons
  5. the gallons of paint converted to litres of paint
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