Paint calculator: how much paint do I need?
Free paint calculator: litres and cans from your own label. No sign-up.
What you're painting
Numbers without a unit are
What your can says
Coats
AREA TO PAINT
Turn on JavaScript and this works out your paint as you type. The formula is below if you'd rather do it by hand.
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How the paint calculator works
Type the room the way your tape reads. Feet and inches, a plain 12.5, metres, centimetres: the calculator reads every length back beside its label before it multiplies anything. That readback is where a window typed as 48 feet instead of 48 inches gets caught, and caught is better than paying for it.
The walls are the room's distance around times its height: 2 × (length + width) × height. Each door and window you won't paint comes off at the size you measured. We don't assume a door size: closets, patio doors and front doors all differ. The ceiling is length times width, and it stays out until you switch it on. Every conversion runs on the definitions in Canada's Weights and Measures Act, where an inch is exactly 2.54 cm.
Then your label takes over. Both Canadian labels we read print coverage per can, as a range: Benjamin Moore's Canadian page for Regal Select eggshell says "37-42 m²/3.79 L can". Type it in exactly as printed. The page multiplies your area by your coats when every coat uses the same coverage. With a separate first-coat figure, it divides the area by that once and adds the later coats at the topcoat rate. It works both ends of a range and rounds up to whole cans once, at the end.
That last part matters more than it sounds. Walls and ceiling in the same paint are added before rounding. Take a 3 by 3 metre condo bedroom with 2.5 metre walls, two coats, a label that says 40 m² a can: the walls need 1.50 cans' worth and the ceiling 0.45. Round each one and you buy three cans. Add them first and it's two.
We hold no coverage figure of our own and we don't pick your coats. Nor do we slip in a waste percentage. If your label gives a separate figure for the first coat, there's a field for that too.
Who this is for
- Homeowners about to paint a bedroom, a freshly drywalled basement or a condo before it goes on the market, with a tape-measure reading in one hand and a can in the other.
- Anyone holding a painter's quote that says "4 cans" who wants to know whether that fits the room.
- People who measured in feet and bought a can that speaks metric.
Homeowner questions about paint and coverage
How much paint do I need for a bedroom?
For a 12' 6" by 10' 9" bedroom with 8-foot walls, one door and one window, two coats from a label that says 36 to 40 m² per can come to two 3.78 L cans. That room has 31.90 m² of wall to paint, and two coats take 1.77 to 1.59 cans' worth, so it's two at either end of the range. Paint the ceiling in the same paint and it climbs to three. Your label decides it, so type yours.
How much paint do I need for a 12x12 room?
About two 3.78 L cans for the walls, or three with the ceiling, going by one label we read. A 12 by 12 foot room with 8-foot walls has 384 square feet of wall (35.67 m²) before doors and windows. Benjamin Moore's Canadian page for Regal Select eggshell prints 37-42 m² per can, so two coats need 1.93 to 1.70 cans' worth. Add the ceiling and it's 2.65 to 2.34: three cans.
How much does a 3.78 L can of paint cover?
Whatever its label says, and labels differ more than you'd think. Benjamin Moore's Canadian page for Regal Select eggshell gives 37-42 m² per can. Sico's data sheet for Evolution pearl gives 47 to 53 m² per 3.78 L as a topcoat, and 44 to 49 m² as a primer coat or on porous surfaces. Sico says its figures leave out what's lost to rough or porous walls and to how you apply the paint.
How many litres are in a gallon of paint?
The can most of us call a gallon holds 3.78 L. That's just under a US gallon, which is 3.785 L by the US definition of 231 cubic inches. Canada's own gallon, the imperial one in the Weights and Measures Act, is 4.546 L. One Benjamin Moore page even calls the same can 3.78 L in its size list and 3.79 L in its coverage line. We count cans straight from coverage per can, so the mismatch never adds one.
How many coats of paint do I need on walls?
We don't pick that for you, and the arithmetic can't either. Benjamin Moore's Regal Select data sheet requires two coats on bare surfaces; previously painted walls can take one or two. Sico warns that some colours or drastic colour changes may need another coat. Until you choose, the calculator shows one, two and three side by side, so you can see whether that third coat costs you another can.
How many coats of paint on new drywall?
Check the label: some print a lower figure for a first coat on a bare surface. Sico's sheet for Evolution gives 44 to 49 m² per 3.78 L as a primer coat or on porous surfaces, against 47 to 53 for the coats after, and says two coats are required on an uncoated surface, the first acting as the primer. Take a 7.2 by 5.8 metre basement room with 2.7 metre walls: 44 then 47 instead of 47 throughout turns three cans into four.
How much paint do I need for a ceiling?
Measure length times width and treat it like a wall: area times coats, divided by the coverage per can. If the ceiling gets the same paint as the walls, add the two before you round. In a 3 by 3 metre condo bedroom with 2.5 metre walls, at 40 m² a can and two coats, the walls need 1.50 cans' worth and the ceiling 0.45. Rounded separately, that's three cans. Added first, it's two.
What do I do with leftover paint?
Keep a little for touch-ups and recycle the rest. Just don't pour it out. Sico's sheet puts it plainly: "Do not pour down a drain or storm sewer." In eight provinces (British Columbia, Saskatchewan, Manitoba, Ontario, New Brunswick, Prince Edward Island, Nova Scotia, and Newfoundland and Labrador), Product Care Recycling takes leftover paint free at its drop-off sites, in the original can with the label on. Anywhere else, ask your municipality.
How much paint do I need?
Area, coats, coverage, then whole cans. Measure each room's walls as 2 × (length + width) × height, take off what you won't paint, and add the ceiling if it's getting the same paint. If every coat uses one coverage figure, multiply by your coats and divide by that figure. With a separate first-coat figure, divide the area by that once, then add the later coats at the topcoat rate. Work both ends of a range and round the cans' worth up once, at the end.
Litres come from the can size, so a paint calculator that shows litres should show the can it used. Ours puts the litres beside the cans, adds a US-gallon figure for anyone who still thinks in gallons, and never asks you for one. If your label gives its coverage in square feet, pick sq ft and type the figure as printed. The conversion shows up under the field.
Sources and last checked
Checked October 8, 2026. Data version paint-ca-2026-10-07.
- Unit definitions: Weights and Measures Act, R.S.C. 1985, c. W-6, Schedules I and II (Justice Laws website, current to 2026-09-21); the US gallon from NIST Handbook 44 (2026), Appendix C.
- Coverage figures quoted in the answers above: Benjamin Moore Canada, Regal Select Interior Paint, Eggshell, product page and its linked Canadian F549 data sheet; Sico Evolution 866-5XX technical data sheet, edition 02/2018, still linked from Sico's current product page and published by PPG Architectural Coatings Canada.
- Paint recycling: Product Care Recycling, "Recycle Your Paint" page.
How we made it: the calculator only does arithmetic on the numbers you type. It keeps no coverage figures, coats or prices of its own. We name the makers above for what they publish, not to recommend them.
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