How to estimate paint for your room
Painting an interior room comes down to one number: how many gallons to buy. Enter the length, width, and wall height and the calculator finds your total wall area, subtracts the doors and windows you will not paint, multiplies by your coats, and divides by coverage.
Interior wall paint covers about 350 square feet per gallon on smooth, previously painted drywall, so that is the default. New or textured walls drink more paint, so drop the coverage in Advanced if your walls are thirsty.
Coverage cheat sheet
| Surface / situation | Approx. coverage per gallon |
|---|
| Smooth, previously painted surface | 350 to 400 sq ft |
| New or bare wood / drywall (thirsty) | 250 to 350 sq ft |
| Textured, rough, or weathered | 200 to 300 sq ft |
| Primer | 200 to 300 sq ft |
This tool defaults to 350 sq ft per gallon for a room. Change it under
Advanced if your surface is rougher or more porous than average.
Frequently asked questions
How much paint do I need for a 12x12 room?
A 12 by 12 room with 8-foot walls has about 384 square feet of wall. After subtracting a door and a couple of windows and applying two coats, you need roughly 2 gallons at 350 sq ft per gallon coverage.
How many coats of paint do I need?
Plan on two coats for most rooms. One coat can work when repainting the same color over a clean, sound surface; budget three coats for drastic color changes or inexpensive paint that does not cover well.
How many square feet does a gallon of paint cover?
One gallon of interior wall paint typically covers 350 to 400 square feet in a single coat. Textured, porous, or dark-to-light surfaces cover less, so this calculator uses a conservative default to keep you from coming up short.
Should I buy extra paint?
Yes. Keep a little for touch-ups. Rounding up to full gallons usually gives you enough of a cushion; for large jobs, add roughly 10 percent so you have a color-matched can on the shelf later.