Ceiling Paint Calculator
Calculate how many gallons of ceiling paint you need from the room size, number of coats and ceiling texture. Popcorn and textured ceilings soak up more paint.
By CalcBuilt Editorial TeamUpdated September 11, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Ceiling paint needed
- 0.82 gal
- Buy 1 gallon for 2 coats
- Ceiling area
- 144 sq ft
- Smooth ceiling, no texture allowance
- Per coat
- 0.41 gal
Ceiling Paint formula
Ceiling area = Length x Width + extra areas
Effective area = Ceiling area x texture factor (smooth 1.0, light texture 1.15, popcorn 1.35)
Gallons = Effective area x Coats / Coverage per gallon (typically 350 to 400 sq ft)Worked example
A 14 x 18 ft living room with a popcorn ceiling, two coats: 14 x 18 = 252 sq ft. Popcorn texture factor 1.35 makes it paint like 340 sq ft. Two coats at 350 sq ft per gallon: 340 x 2 / 350 = 1.94 gallons, so buy 2 gallons.
Quick reference
| Ceiling size | Area | Gallons needed | Gallons to buy |
|---|---|---|---|
| 10 x 10 ft | 100 sq ft | 0.57 | 1 |
| 12 x 12 ft | 144 sq ft | 0.82 | 1 |
| 12 x 15 ft | 180 sq ft | 1.03 | 2 |
| 15 x 20 ft | 300 sq ft | 1.71 | 2 |
| 20 x 20 ft | 400 sq ft | 2.29 | 3 |
How to calculate ceiling paint
A ceiling is a single flat area: length times width in feet, plus any hall or closet ceiling painted the same color. Divide by 350 square feet per gallon for a sound painted ceiling, or 250 to 300 for a first coat on bare drywall, and multiply by the coats.
Texture is the variable most people miss. Knockdown and orange peel add about 15 percent to the surface the roller has to cover; popcorn adds 35 percent or more.
Choosing ceiling paint
Dedicated ceiling paint is dead flat and high build, so it hides seams and roller marks and spatters less overhead than wall paint. Bare drywall gets PVA primer first. A water stain bleeds through any number of latex coats: fix the leak, then spot prime with Zinsser BIN or Kilz Original.
Paint the ceiling first, then walls, then trim. Cut in with a 2-1/2 in sash brush, roll toward the main window and keep a wet edge; flat paint that dries between passes shows a lap mark. Nap: 1/2 in on smooth drywall, 3/4 in on knockdown, 1 in or more on popcorn. Over 3 gallons, buy a 5 gallon bucket, one batch and cheaper per gallon.
What this calculator leaves out
Primer (PVA at about 300 sq ft per gallon, stain blocker on stains), wall and trim paint, roller covers, an extension pole and drop cloths. Popcorn removal and retexturing are separate jobs, and popcorn from before 1980 needs an asbestos test first.
Mistakes that cost money
- Rolling wall eggshell on a ceiling: every drywall seam shows under window light; use flat ceiling paint, which also spatters less overhead.
- Painting over a water stain with latex: the tannin bleeds through two coats; spot prime with shellac or oil-based stain blocker after fixing the leak.
- Re-rolling an unpainted popcorn ceiling: wet texture falls off in sheets; spray it or make one light pass with a 1 in nap.
- Scraping or sanding popcorn from before 1980 without a test: it may contain asbestos; a lab test typically runs $30 to $60.
- Walls first, then the ceiling: roller spatter lands on the finished walls; paint the ceiling first and cut the wall color into the ceiling line.
- A 3/8 in nap on knockdown skips the low spots and leaves holidays; use 3/4 in on texture and 1 in or more on popcorn.
Key facts
- Flat ceiling paint covers about 350 to 400 sq ft per gallon per coat on smooth drywall.
- Popcorn and heavily textured ceilings use 25 to 40% more paint than smooth ceilings.
- One gallon covers a 12 x 12 ft smooth ceiling with two coats and leaves a little for touch-ups.
- Use a 1/2 in nap roller on smooth ceilings and a 3/4 in or thicker nap on texture.
- Paint the ceiling before the walls so drips and roller spray land on unpainted wall.
Frequently asked questions
How much paint do I need for a 12x12 ceiling?
About 0.82 gallons for two coats on a smooth ceiling, so one gallon is enough. A popcorn ceiling of the same size needs about 1.1 gallons, so buy two.
How do I paint over a water stain on the ceiling?
Fix the leak first, then spot prime the stain with a shellac-based or oil-based stain-blocking primer such as Zinsser BIN or Kilz Original. Latex primer and ceiling paint do not block the tannin, so the stain returns through two coats. Then paint the whole ceiling, not just the patch, so the sheen matches.
Do ceilings need two coats?
Two coats for new drywall, stains, or a color change. One coat is usually fine when refreshing an existing white ceiling with a quality flat ceiling paint.
Can I use wall paint on a ceiling?
You can, but flat ceiling paint hides imperfections and roller marks better and spatters less. Wall paint in eggshell or satin will show every seam under raking light.
Sources and references
- BEHR Premium Plus Interior Ceiling Flat Paint and Primer product page (Behr)
- Premium Ceiling Paint product page (Sherwin-Williams)
- Waterborne Ceiling Paint 508 technical data sheet (Benjamin Moore)
Next steps for this project
The usual order for a paint & walls project. See all paint & walls calculators.
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.