Paint Calculator
Estimate how many gallons of paint you need for any room. Just enter your measurements.
Why this much?
Estimate based on the measurements you entered and standard paint coverage. Actual coverage varies by product and surface, so check your paint can’s label.
How the calculator works
This calculator adds up the area of your four walls (length + width, doubled, times ceiling height), then subtracts a standard allowance for doors (about 20 sq ft each) and windows (about 15 sq ft each) so you’re not paying for paint you won’t use.
Most interior paints cover roughly 350 square feet per gallon on a smooth, primed wall. We multiply your wall area by the number of coats you plan to apply, divide by 350, and round up to the nearest whole gallon so you don’t run out mid-wall.
Quick tips for painting a room
- Always round up. Running out of paint mid-wall creates visible touch-up lines once it dries.
- Buy a bit extra for future touch-ups. Paint formulas change over time, so an extra pint now can save a mismatched wall later.
- Two thin coats beat one thick one. Thick coats drip, take longer to dry, and often need sanding back.
- Dark-to-light transitions need more coats. If you’re painting over a bold color with a light one, budget for a third coat or a tinted primer.
- Textured walls drink more paint. Stucco, popcorn, or heavily textured drywall can use 20–30% more paint than a smooth wall.
Typical paint coverage
| Paint type | Coverage per gallon |
|---|---|
| Standard interior paint (smooth wall) | 350–400 sq ft |
| Primer | 200–300 sq ft |
| Textured or stucco walls | 250–300 sq ft |
| Ceiling paint | 300–350 sq ft |
| Exterior masonry paint | 250–300 sq ft |
Frequently Asked Questions
Do I need to paint the ceiling too?
This calculator only estimates wall paint. Ceilings are usually a different (flatter) paint and are calculated separately using the room’s floor area instead of wall height.
How many coats do I actually need?
Two coats is standard for most color changes and gives the most even, durable finish. One coat can work for a fresh coat of the exact same color in good condition.
Should I subtract closets?
This calculator treats the room as one open box. For rooms with closets, measure the closet walls separately and add that area to your total if you’re painting inside them too.
What if my result is a fraction of a gallon?
Paint is typically sold in quarts and gallons. If you need just over a whole number of gallons, it’s usually more economical to round up to the next full gallon rather than buying a gallon plus a quart.