One gallon of paint covers about **350 square feet** per coat. That sounds simple until you factor in doors, windows, multiple coats, and waste. You don’t want to run out mid-roller, so here’s the exact method to calculate how much paint you need for any room.
How Much Paint Do You Need for One Room?
Calculate your total wall area (perimeter times ceiling height), subtract doors (**21 sq ft each**) and windows (**15 sq ft each**), multiply by the number of coats, then divide by **350**. Add **10%** for waste from spills and touch-ups. A standard **12x14 foot** bedroom with **8-foot ceilings**, two doors, and three windows has about **390 sq ft** of paintable wall space.
Paint Coverage by Room Size
| Room Size | Paintable Area (2 coats) | Gallons Needed | Buy |
|---|---|---|---|
| 10x10 bedroom | ~360 sq ft | 2.3 gallons | 1 gal + 2 qt |
| 12x14 bedroom | ~440 sq ft | 2.8 gallons | 3 gallons |
| 14x18 living room | ~550 sq ft | 3.5 gallons | 4 gallons |
| 20x20 master | ~720 sq ft | 4.5 gallons | 5 gallons |
These estimates include the **10% waste buffer** and assume standard door and window counts. Always round up to the nearest gallon or quart -- leftover paint is great for touch-ups later.
Why Two Coats Matter
The first coat seals the surface and provides a base. The second coat delivers even color and full coverage. One coat usually leaves thin spots and uneven sheen, especially when you're covering dark colors with light paint.
Going from a dark to light color may require **3 coats**. Use a primer on bare drywall to reduce the number of finish coats needed.
Choosing the Right Paint Finish
Painting a room this weekend?
Use the Paint Coverage Calculator to get the exact gallons and quarts you need for any room. Enter your dimensions, doors, windows, and number of coats.