Ceiling paint calculator
Ceilings are the easy measure: length times width, no doors to subtract. The texture is what moves the number. Smooth drywall sips; popcorn gulps.
How the math works
Ceiling area is the room's footprint, length times width. A 12x12 room is 144 sq ft overhead; two coats is 288 sq ft of spreading, which at 350 sq ft per gallon comes to 0.8 gallons. Buy one. The texture options change the divisor: 300 for orange peel, 250 for popcorn, because textured surfaces carry more paint per pass and eat into the can faster than the smooth-wall math admits.
For vaulted or cathedral ceilings, measure the actual sloped planes, not the footprint. A 12x12 room under a 30-degree vault has about 166 sq ft of ceiling, not 144.
Questions people ask
How much paint does a 12x12 ceiling take?
One gallon for two coats: 144 sq ft twice over is 288 sq ft of spreading, and flat ceiling paint covers about 350 sq ft per gallon on smooth drywall. One coat of the same white on a clean ceiling squeaks by on 2 quarts, but buy the gallon (three quarts costs more).
Does popcorn texture really need more paint?
A lot more. Heavy texture roughly doubles the surface the roller actually touches; plan on 250 sq ft per gallon and a thick 3/4-inch nap. Never roll a previously sprayed, unpainted popcorn ceiling hard: it can peel off in sheets. Light passes or a sprayer.
One coat or two on a ceiling?
Two if the ceiling has water stains (after a stain-blocking primer), smoke residue, or you are changing the shade. One coat hides fine when it is the same white going over sound, clean paint. Ceilings forgive more than walls because nobody puts a lamp against them.
Can I use wall paint on the ceiling?
You can, but flat ceiling paint exists for a reason: it hides roller marks on the most raking-light surface in the house and it spatters less. Eggshell overhead shows every lap line at sunset.