Ceiling paint calculator
Ceiling paint calculator:
gallons, primer and cost
A ceiling is not a wall lying down. Flat ceiling paint covers less per gallon, and a popcorn or knockdown finish has far more surface than its plan area suggests. This works both into the gallons, and measures the cut-in separately.
Enter measurementsOptional
What will it cost?
Every material the calculator worked out gets its own price. Each field starts at a typical US figure so you have something to work from — change any of them to what your own supplier charges.
These prices are approximate. They are national US retail figures, and what you actually pay varies with your region, your supplier, the season and how much you buy at once. Treat them as a starting point, not a quote — always price the job from your own supplier's current figures before you order.
Your prices
More in this series
The rest of the paint job
Walls and ceilings are painted in the same visit but bought in separate cans. Work out both before the trip to the store.
Based on your result
What you'll need
Quantities update after every calculation. A textured ceiling wants a thicker nap than a smooth one.
- Ceiling paint
- Gallons for every coat, texture included
- Calculate above
- Stain-blocking primer
- Whole-ceiling coat where marks show
- —
- Roller covers
- Nap thickness to suit the texture
- —
- Painter's tape
- Along the wall line where you cut in
- —
- Extension pole
- Saves the ladder and your shoulders
- 1 pole
The maths
How this ceiling paint calculator works
Two things separate a ceiling from a wall. Flat ceiling paint goes on heavier so it does not flash under side light, which costs about an eighth of its coverage; and a textured ceiling has real surface area the plan measurement never sees.
surface = ceiling area × texture factor
gallons = ⌈ surface × coats ÷ 350 sq ft ⌉
cut-in = 2 × (width + length)
- ×1.00
- smooth
- ×1.15
- knockdown
- ×1.30
- popcorn
- 01
Measure the ceiling
Width times length, the same footprint as the floor below it.
- 02
Take out the openings
A skylight, a fan housing or a light tray the roller never crosses, each measured on its own.
- 03
Apply the texture factor
Popcorn adds about 30% more surface than its plan area, knockdown about 15%. This is the step a wall calculator has no reason to do.
- 04
Divide by ceiling coverage
About 350 sq ft a gallon, not the 400 a wall gets — flat ceiling paint is laid on heavier so it does not flash.
- 05
Prime the whole ceiling if anything is stained
A spot-primed water mark flashes through the finish and shows as a bright rectangle. Block the lot or none of it.
- 06
Measure the cut-in on its own
A ceiling has far more edge per square foot than a wall, and brushing that line is where the time goes.
Good to know
Ceiling paint questions, answered
A 12 by 12 ceiling is 144 sq ft. Smooth and in two coats that is 288 sq ft of coverage — one gallon does it at the 350 sq ft a gallon flat ceiling paint gives. Make it a popcorn ceiling and the same room needs two, because the texture adds about 30% more surface.
Because it is meant to be laid on heavier. Ceilings catch light across their surface rather than down it, so every thin patch and roller lap shows. Flat ceiling paint is formulated thick and matte to hide that, and the price of hiding it is coverage — about 350 sq ft a gallon against 400 for a wall finish.
Yes, with a stain-blocking primer, and over the whole ceiling rather than the mark. Tannin and water stains bleed straight through ordinary paint however many coats you put on. Spot-priming works on the stain but the primed patch takes the finish coat differently and shows as a bright rectangle under the light.
About 30% more than a smooth one of the same size, because you are painting the whole surface of every peak and valley rather than a flat plane. Knockdown and orange peel sit around 15%. Roll it with a thick nap, 3/4 in or more, and work slowly — a popcorn ceiling sheds if you scrub at it with a wet roller.
It will cover, but it will show every lap mark. Wall paints have more sheen and a longer open time tuned for vertical work; on a ceiling that reads as streaks wherever two wet edges met. Dedicated ceiling paint is flat, thick and often goes on pink so you can see where you have been.
Two over anything that has been painted before, and two over new primed drywall. One coat only works when you are refreshing the same colour on a sound, smooth ceiling and even then the laps tend to show. Cut in each coat before you roll it, not all the cutting first.
Ceiling first, always. It is the messiest part of the room, and anything that runs down the wall gets covered by the wall coats afterwards. Do it before the floor goes down too, if the order is yours to choose.