How Much Paint for a Ceiling?

Updated November 1, 2026

Ceiling paint is the ceiling’s length times its width, times the number of coats, divided by the coverage printed on the can. Gallons come last. The Paint Calculator is four walls only. It asks for wall height, subtracts doors and windows, and has no ceiling field. Typing the room into that form counts walls and leaves the ceiling out.

Measure the ceiling you will paint

Measure the length and width of the ceiling surface in feet. On a flat rectangular ceiling that is the same footprint as the floor. Measure to the walls you will cut in against, not out to a closet you are leaving for another day.

A soffit or a dropped tray that you are not painting is not part of this rectangle. Measure the flat surface you will roll. A ceiling fan or a small can light is not worth subtracting. A skylight or a large opening you will not paint can come off the area. The well of a skylight, if you paint those sides, is extra area, not a subtraction.

Coats and the number on the can

Two coats is the usual plan on a color change or on a ceiling that has been patched. One coat is sometimes enough when the new paint matches what is already there and the can says one coat will hide. Multiply the ceiling area by the coats before you divide.

Divide by the coverage on the can, in square feet per gallon. 350 is a common interior figure and the number the wall calculator starts with. It is not a property of your ceiling. Flat ceiling paint on a textured surface, or a deep color over white, often covers less. Type the number from the can you are buying.

A 12 by 15 foot ceiling, two coats

One flat ceiling, 12 feet by 15 feet, two coats, 350 square feet per gallon.

• Ceiling area: 12 × 15 = 180 sq ft.
• After two coats: 180 × 2 = 360 sq ft.
• Gallons before waste: 360 ÷ 350 = 1.03 gallons.

1.03 gallons is two full coats on that ceiling, with nothing left in the tray and nothing spilled. You still add a waste allowance, then round up to a whole gallon. One gallon does not cover it.

Add waste, then buy whole gallons

The waste choices on the wall calculator are 0, 5, 10, 15, and 20 percent. Use the same set here. Waste is paint that stays in the roller, the tray, and the cut line. It is not a second ceiling.

• 5% — a smooth ceiling, a similar color, and careful cutting-in.
• 10% — the usual ceiling. 1.03 × 1.10 = 1.13 gallons.
• 15% or 20% — a textured ceiling, a large color change, or touch-up you expect to pull from the same cans.

1.13 gallons rounds up to 2 gallons. One gallon finishes neither the second coat nor the waste you allowed. An unopened gallon of the same tint can often go back. A ceiling that flashes because you ran out mid-span cannot. Buy both gallons in one trip so the store mixes one batch, and keep the formula sticker.

Do not enter wall height for this ceiling

The paint calculator’s wall area is 2 × (length + width) × wall height, then minus doors and windows. There is no switch that turns those fields into a ceiling. If you enter this 12 by 15 foot room with an 8 foot wall height, zero doors, zero windows, two coats, 350 square feet per gallon, and 10 percent waste, the tool does this:

• Gross walls: 2 × (12 + 15) × 8 = 432 sq ft.
• After two coats: 432 × 2 = 864 sq ft.
• Before waste: 864 ÷ 350 = 2.47 gallons. With 10 percent waste: 2.72 gallons, which rounds up to 3 gallons.

Those 3 gallons are the four walls with no openings. They are not the ceiling, and they are already more than the 2 gallons this ceiling needs. A real room would also subtract doors and windows, and the result would still be a wall order. The four-wall walk-through, including that subtraction, is How to Calculate Paint for One Room.

What these 2 gallons leave out

The walls are a separate purchase. Primer is a different can. These 2 gallons do not include it. A closet ceiling is another small rectangle. Run the same length × width math for it, or the closet stays the old color.

A skylight you will not paint can come off the 180 square feet. A 2 by 4 foot opening is 8 square feet. Two coats make that 16 square feet, so the coated area is 360 − 16 = 344. 344 ÷ 350 = 0.98 gallons, and 10 percent waste is 1.08 gallons, which still rounds up to 2 gallons. On this ceiling the opening does not change the cans you carry out.