Paint Calculator
How much paint do you need for that room?
How this is calculated
- Total wall area = 2 × (length + width) × height
- Deduct 20 sq ft per door and 15 sq ft per window
- Paintable area × coats ÷ coverage per gallon = exact gallons
- Buy amount is rounded up to the nearest half gallon — unmixed paint can differ slightly between cans, so avoid needing a third can mid-wall.
Common questions
How much paint do I need for a 10×10 room?
A 10 × 10 ft room with 8 ft ceilings has 320 sq ft of wall. With two doors and two windows deducted, that is about 270 sq ft paintable — and two coats at 400 sq ft per gallon works out to roughly 1.4 gallons, so buy 1.5. If you are painting the ceiling too, add a gallon for it.
How much does a gallon of paint cover?
One gallon of typical interior latex covers 350–400 sq ft per coat — a 10 × 10 room's four walls with one coat. Textured or unprimed drywall absorbs more and can drop coverage to 250–300; a primer coat first restores the label number.
Do I really need two coats?
For a color change, almost always — single-coat coverage is a label ideal, not a real-world result over a different base color. Same-color touch-ups, fresh drywall after a quality primer, or deep-base paints labeled one-coat can genuinely go single.
Should I deduct doors and windows?
Yes, but keep the paint. Doors and windows typically account for 10–15% of a room's wall area, and having a little extra for cut-ins, touch-ups, and the trim itself is usually welcome. If your openings are unusually large (picture windows, French doors), measure them and let the deduction work for you.
Does a gallon really cover 400 sq feet?
On smooth, primed drywall with a good roller, yes. Rough surfaces, stucco, bare wood, or dark-over-light paint jobs all cut that figure. If you are between amounts, buy the larger size — most stores take unopened cans back.