How much paint you need
Paint quantity is gallons = wall area × coats ÷ coverage per gallon. With 875 sq ft, 2 coats and 350 sq ft per gallon you need 5 gallons. Most interior paints cover 300–400 sq ft per gallon. Wall area comes from the square footage calculator if you have not measured yet.
How to use this calculator
Enter total wall area, number of coats, and the coverage printed on the can. To get wall area, multiply perimeter by ceiling height; the drywall calculator uses the same area input.
Coverage tips
Rough or porous surfaces drink more paint, so coverage drops. Primer counts as a coat. Two coats is standard for color changes. Trim and baseboards are figured separately — see the baseboard calculator for linear footage.
Colour matters as much as area. Covering a dark wall with a pale shade can take three coats unless you prime with a tinted primer first, while refreshing a similar colour may need only one. Buy all the paint for a room in one go, or ask the store to box the cans together, because tint batches vary just enough to show as a band where you stop and restart. Bare drywall and fresh filler both drink the first coat, so prime them before you count coverage.
Frequently asked questions
- How do I calculate how much paint I need?
- Multiply wall area by the number of coats, then divide by the coverage per gallon printed on the can.
- How much does a gallon of paint cover?
- Typically 300–400 sq ft per coat on smooth surfaces; rough or porous walls cover less.
- Do I need to subtract doors and windows?
- For small rooms you can ignore them; for larger walls subtract big openings to avoid over-buying.
- How many coats should I apply?
- Two coats is standard, especially for color changes. Primer counts as an extra coat.
- How do I work out paint for a ceiling?
- Multiply the ceiling length by its width and add that to your wall area, or run it as a separate calculation. Ceilings are usually flat-finish paint, and textured ones absorb noticeably more than the label figure.