How Much Paint Do I Need for My Room?
You’ve decided on your favourite Benjamin Moore paint colours — now it’s time to figure out how much paint you need.

Because wall surfaces can differ, paint coverage highly depends on texture, porosity, and surface condition.
The experts at your local
Toronto West paint store recommend the following when calculating how much paint you need for your interior walls.
How much does 1 gallon of paint cover
General Guideline
How to calculate your surface area:
- Determine the square footage: A simple measurement of width times height for each wall in your space (don’t forget the ceiling)
- Deduct doors and windows: Measure all doors and windows to get their square footage so you can deduct them from the total area
- Door frames and window trim: Frames and trim are often a different colour. Measure them the same way to get the square footage so you know how much trim paint to buy
The following is an approximation of surface coverage for different types of paint on walls in good condition with no texture and a two-coat application:
- Ceiling paint, one gallon, covers 350 - 400 square feet
- Primer, one gallon, covers 225 - 275 square feet
- Wall paint, one gallon, covers 375 - 425 square feet
- Trim paint, one gallon, covers 375 - 425 square feet
Dramatic Paint Colour Change
When painting over a dark colour with a lighter colour, you need extra coats of paint. However, using a primer for your initial coat drastically reduces the amount of paint you need for total coverage. And primer is generally less expensive than your coloured interior paint.
Colour on New Drywall
New drywall is very porous, so it soaks up a lot of paint. If you’re painting a room with new drywall, use a coat of primer to help prepare the surface for your colour and cut down on how many coats you need for proper coverage.
Textured Walls
Textured walls like stipple, stucco, popcorn ceilings, or brick mean more surface area; therefore, you need more paint than your square footage measurements initially indicated. When calculating how much you need for textured surfaces, add an extra 20%.
Ask the Experts at Your Local Toronto West Paint Store
Looking for trusted advice from your local West Toronto paint store?
Get in touch with Paint Colours Unlimited. We specialize in helping you choose the best colours and can determine the right amount of paint for your next project.