Paint guide
How Much Paint Do I Need?
The amount of paint you need depends on the size of the room, wall height, number of coats, paint coverage, and how many doors and windows you subtract.
Calculate wall area, subtract doors and windows, multiply by the number of coats, then divide by the paint coverage rate.
Use the Paint Calculator →Paint Formula
Most interior paints cover about 300–400 square feet per gallon. New drywall, textured walls, or major color changes may need more paint.
Paint Needed for Common Room Sizes
| Room Size | Typical Paint Needed | Assumption |
|---|---|---|
| 10 × 10 ft | 1–2 gallons | 2 coats, standard walls |
| 12 × 12 ft | 2 gallons | 2 coats, standard walls |
| 15 × 15 ft | 2–3 gallons | 2 coats, standard walls |
| 20 × 20 ft | 4–5 gallons | 2 coats, standard walls |
Example
A 20 ft by 15 ft room with 8 ft walls has a perimeter of 70 ft. The wall area is 70 × 8, or 560 square feet. After subtracting one door and two windows, the paintable area is about 509 square feet. For 2 coats, that becomes 1,018 square feet. At 350 square feet per gallon, you need about 3 gallons.
Should You Buy Extra Paint?
Yes. It is usually smart to round up to the next full gallon. Extra paint helps with touch-ups, uneven coverage, roller waste, brush waste, and future repairs.