Paint Calculator for a Room: Gallons for Walls, Ceiling and Trim
Work out how much paint a room needs: walls minus doors and windows, ceiling and trim, each with its own coats, rounded to cans you can buy, with an optional cost. Feet or metres, gallons or litres.
Paint quantity estimate only. It is not a structural, safety or code check. Values marked UNSOURCED are built-in defaults that no paint maker has confirmed here: type the coverage from your own can.
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Nothing is sent until you press Send. Your measurements are included only if you tick the box, and you can see the full report below first.
When to use this
- You are about to paint a room and want to know how many cans of wall, ceiling and trim paint to buy.
- You already know the wall area from another tool, such as wallpaper or drywall, and want to carry it over.
- You want the coats, the cans and the cost on one screen.
How to use
- Choose feet or metres. Enter the room length, width and ceiling height, and the doors and windows.
- Or type a wall area you already have. It replaces the walls above.
- Add trim length and face width if you will paint trim. The baseboard tool on this site gives the length.
- Type the coverage from your can and the number of coats for walls, ceiling and trim.
- Press Calculate paint and copy the buy list.
Examples
- 12 x 10 x 8 ft room, one door, one window, ceiling, 2 coats at 350 ft² per gallon: The walls are 322 ft² after the door and window. With 5 percent extra that is 1.93 gallons, so buy two 1 gallon cans. The ceiling needs 0.72 gallons, so three quarts.
- 500 ft² of wall typed in, 2 coats at 400 ft² per gallon: That is 2.5 gallons, or 2.63 with 5 percent extra. The plan buys 2 gallons and 3 quarts instead of a full third gallon.
Understanding the result
Each surface is worked out on its own because walls, ceiling and trim are often different paint. The area is multiplied by the number of coats and divided by the coverage of one coat, then the extra for loss is added. The result is matched to the can sizes in the table so you buy the least paint that still covers the need, and with the fewest cans when two mixes hold the same amount.
Limitations
- This is a paint quantity estimate. It does not judge surface prep, safety, ventilation or local rules.
- Rough, dark or porous surfaces and big colour changes can need more paint or a primer coat. Add a primer as extra coats on the surface.
- Rooms that are not rectangles, sloped ceilings and textured walls are not modelled. Type your own wall area instead.
- Read the label of your paint. It is the best source for coverage and the number of coats.
FAQ
How much paint do I need for a room?
Find the wall area, take off doors and windows, multiply by the coats and divide by the coverage on the can. A 12 x 10 x 8 ft room with a door and window needs about 1.9 gallons for two coats on the walls.
How many gallons of paint cover 400 square feet?
At 350 square feet per gallon one coat of 400 square feet needs about 1.14 gallons, so two coats need about 2.3 gallons. Use the coverage from your own can.
Do I paint the ceiling and walls with the same can?
Often not. Ceiling paint is usually a different product, so the tool shows walls, ceiling and trim separately.
Should I take doors and windows off the wall area?
Yes for large openings. The tool does this for you. If you type a wall area yourself, type it after any deductions.
How many coats of paint do I need?
Two coats is common. A small colour change on a clean wall may need one; a dark colour or bare surface may need three or a primer.
Does this tool store my measurements?
No. It runs in your browser. The share link keeps your numbers after the # sign, which is never sent to a server.
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