Calculator
Paint Calculator: How Much Paint Do I Need for a Room?
Free paint calculator: enter room size, doors, windows and coats to find how many gallons or liters of wall and ceiling paint (and primer) you need.
How the paint calculator works
It calculates the wall area as the room perimeter multiplied by the wall height, subtracts standard doors (about 21 sq ft / 1.9 m²) and windows (about 15 sq ft / 1.4 m²), multiplies by the number of coats and divides by the coverage of your paint. Check the coverage on the can — it's usually printed as sq ft per gallon or m² per liter.
Tips for buying paint
- Round up to full cans. A little leftover is great for touch-ups.
- Dark or saturated colors may need an extra coat or a tinted primer.
- Textured walls can use 10–25% more paint.
- Mix all cans together ("boxing") before starting for perfectly even color.
Next: learn the method in how to paint a room like a pro.
Frequently asked questions
How much area does a gallon of paint cover?
Typically 350–400 sq ft per gallon (about 9–11 m² per liter) for one coat on smooth, primed walls. Textured, porous or unprimed surfaces take more.
How many coats of paint do I need?
Two coats for most walls. Three may be needed for strong color changes, or use a tinted primer first.
Keep reading
How to paint a room like a pro
Prep, cut in, roll, repeat — the full method for crisp lines and no streaks.
12 painting mistakes and how to fix them
Roller marks, bleeding tape lines and blotchy patches — causes and fixes.
Wallpaper calculator
Accurate roll count using the strip method, including pattern repeat.