How Much Paint Do I Need? The Complete Room-by-Room Guide
Most rooms need 1-2 gallons of paint. The formula is simple: (total wall area - doors and windows) divided by 350 equals gallons needed. One gallon covers approximately 350-400 square feet with a single coat.
Need a quick answer? Use our paint calculator to get an instant estimate. But if you want to understand the math and plan your project properly, read on.
The Simple Paint Calculation Formula
Here's the formula professional painters use:
- Calculate total wall area: (Room perimeter × ceiling height)
- Subtract openings: Minus doors (21 sq ft each) and windows (15 sq ft each)
- Divide by coverage rate: 350 sq ft per gallon
- Multiply by number of coats: Usually 2
Example: A 12×14 foot room with 8-foot ceilings, 2 doors, and 2 windows:
- Perimeter: (12 + 14 + 12 + 14) = 52 feet
- Wall area: 52 × 8 = 416 square feet
- Minus openings: 416 - (2 × 21) - (2 × 15) = 344 square feet
- Gallons for one coat: 344 ÷ 350 = ~1 gallon
- For two coats: 2 gallons
Room-by-Room Paint Estimates
Don't want to measure? Here are typical paint requirements based on average room sizes:
| Room Type | Average Size | Paint Needed (2 coats) |
|---|---|---|
| Small Bathroom | 5×8 ft | 1 gallon |
| Large Bathroom | 8×10 ft | 1.5 gallons |
| Small Bedroom | 10×10 ft | 2 gallons |
| Master Bedroom | 14×16 ft | 3 gallons |
| Living Room | 16×20 ft | 3-4 gallons |
| Kitchen | 12×12 ft | 1.5-2 gallons |
Note: Kitchen estimates are lower because cabinets cover significant wall space.
Factors That Affect Paint Coverage
Wall Texture
Textured walls absorb more paint. Reduce coverage estimates by 15-25% for textured surfaces. Orange peel texture might cover at 300 sq ft per gallon, while heavy knockdown texture could drop to 250 sq ft.
Paint Quality
Premium paints have higher pigment concentration and cover better than budget options. A $50 gallon often covers as well as 1.5 gallons of $25 paint, making it more economical in the long run.
Color Changes
Going from dark to light? You may need 3+ coats or a tinted primer. Light to dark is easier but still benefits from tinted primer to reduce coats needed.
Surface Preparation
Unprimed new drywall drinks paint. Always use primer on new surfaces—it's cheaper than an extra coat of finish paint and provides better results.
Why You Should Always Buy 10-15% Extra
Never buy exactly what you calculate. Here's why:
- Touch-ups: You'll need matching paint for future scratches and scuffs
- Waste: Paint left in trays, brushes, and rollers adds up
- Calculation errors: Real rooms rarely match exact measurements
- Color matching: Store-mixed colors are nearly impossible to match later
Store leftover paint in a cool, dry place. Latex paint lasts 10+ years when properly sealed.
Ceiling Paint: How Much Do You Need?
Ceiling paint calculation is simpler—just length × width:
- 10×12 room = 120 sq ft = about 1/3 gallon per coat
- 14×16 room = 224 sq ft = about 2/3 gallon per coat
- 16×20 room = 320 sq ft = about 1 gallon per coat
Pro tip: Ceilings typically need only one coat if using quality ceiling paint, unless covering stains or dark colors.
Frequently Asked Questions
How much does 1 gallon of paint cover?
One gallon of paint typically covers 350-400 square feet with one coat on smooth, primed surfaces. Textured walls, unprimed surfaces, or drastic color changes may reduce coverage to 250-300 square feet per gallon.
Do I need primer before painting?
You need primer when painting over new drywall, stained surfaces, dark colors, or when making a drastic color change (dark to light). Many modern paints include primer, but separate primer provides better results for challenging surfaces.
How much paint do I need for 2 coats?
For two coats, double your single-coat calculation. If one coat requires 2 gallons, you'll need 4 gallons total. Most paint jobs require two coats for even coverage and durability, especially when changing colors.
Calculate Your Paint Needs Now
Ready to get an exact estimate for your project? Our paint calculator does the math instantly. Just enter your room dimensions and we'll tell you exactly how many gallons to buy.
Remember: it's always better to have a little extra paint than to run out mid-project. Buy that extra quart—your future self will thank you when touch-ups are needed.