Paint Calculator

How much paint do you actually need?

A gallon of paint covers ~350-400 square feet at 1 mil thickness in ideal conditions. In real-world conditions — with textured walls, rolling losses, cutting in, and one full coat — figure 250-300 square feet per gallon. This calculator uses 350 sq ft as the per-gallon baseline and rounds up. Always buy slightly extra for touch-ups months later.

How many coats will you need?

• 1 coat: Only realistic if you're going from light color to same light color with a premium "1-coat" labeled paint. In real homes, 1 coat rarely covers evenly.
• 2 coats (standard): What 95% of paint jobs need. Build into your total.
• 3+ coats: When going from dark to light, from red/yellow to anything else, or covering water stains, smoke damage, or strong patterns.

Double your gallons for 2 coats. Triple for 3.

When you need primer separately

• Fresh drywall: Always. The paper soaks paint unevenly without primer.
• Going from dark to light: One coat of primer often saves you a third coat of finish paint.
• Stains, water damage, smoke: Use a stain-blocking primer like Kilz or Zinsser.
• Glossy surfaces: Bonding primer is critical or paint will peel within months.
• Most repaints (latex over latex): Skip primer if surface is clean and color change is moderate.

Paint type by room

• Flat / matte: Ceilings and low-traffic adult bedrooms. Hides imperfections best but can't be scrubbed.
• Eggshell: Living rooms, dining rooms. Slight sheen, wipes clean for occasional marks.
• Satin: Hallways, kids' rooms, kitchens (sometimes). Stands up to washing, moderate shine.
• Semi-gloss: Trim, doors, bathrooms. Wipes clean of soap splashes, mildew-resistant.
• High-gloss: Front doors, accent furniture, cabinet doors. Mirror-like; shows every imperfection.

Don't forget what subtracts from coverage

The calculator subtracts standard door and window allowances, but these add up if you have many:

• Standard door: 21 sq ft. Subtract from wall total per door.
• Standard window: 15 sq ft. Subtract per window.
• Closet (separate paint): Treat as own room (4 walls + ceiling, no flooring).
• Trim/molding: About 6 inches × room perimeter = sq ft. Usually 1 quart per typical bedroom.

Cost-saving tips from pro painters

• Buy contractor packs. 5-gallon buckets are 15-25% cheaper per gallon than 4× 1-gallon cans.
• Use a roller with a 3/8" nap on standard walls — thicker nap holds more paint but stipples; thinner doesn't load enough.
• One color throughout common areas saves money AND lets you use leftover paint for touch-ups for years.
• Spray for big jobs (200+ sq ft). A $200 sprayer rental pays for itself in time on rooms over 400 sq ft.