MiniCalci

Calculators & Converters
Construction & DIY

Paint Calculator

Free paint calculator estimates how many gallons of paint you need for a room. Enter square footage or room dimensions, coats, and coverage rate for an instant gallon estimate.

Total square footage of wall to be painted

Optional: subtract a percentage of the area for windows and doors

How many gallons of paint do I need for this room?

Coverage is area ÷ coverage rate, then you add coats and waste. A typical interior latex in the US covers about 350–400 sq ft per gallon per coat. Primer, dark colors, raw drywall, and cheap paint cover less. This calculator estimates gallons from wall (and optional ceiling) area so you are not short a gallon on the last wall.

What to measure

  • Walls: length × height for each wall, add them, subtract large openings if you want a tighter number (many people skip small windows).
  • Two coats is normal on a color change. One coat is a refresh of the same color on decent walls.
  • Ceilings often use flat paint; walls use eggshell or satin — buy the finish you will actually roll.

Ballpark

A 12×12 room with 8-ft ceilings is roughly 384 sq ft of wall (ignore door/window). At 350 sq ft/gallon and two coats you need about 2.2 gallons — buy 3 gallons or 2 gallons plus a quart rather than stretching.

Related: square footage if you have several rooms, drywall if the walls are not up yet.

Frequently Asked Questions

How much paint do I need for a room?
Calculate your wall area (perimeter x height, minus any deductions for windows and doors), multiply by the number of coats you plan to apply, then divide by the paint's coverage rate (typically 350 sq ft per gallon) to get the gallons needed.
How is paint coverage calculated per room?
Wall area for a rectangular room is 2 x (length + width) x wall height. For example, a 12 ft x 12 ft room with 8 ft walls has a wall area of 2 x (12 + 12) x 8 = 384 sq ft. Multiply by the number of coats to get the total area to cover.
How many gallons of paint do I need for 2 coats?
Multiply your wall area by 2 (for two coats) then divide by the coverage rate, usually about 350 sq ft per gallon. A 384 sq ft wall area with 2 coats needs 768 sq ft of coverage, which is about 2.2 gallons — typically rounded up to 3 gallons since paint is sold in whole-gallon or quart increments.
How do I calculate paint for a 12x12 room?
For a 12 ft x 12 ft room with standard 8 ft walls: wall area = 2 x (12 + 12) x 8 = 384 sq ft. With 2 coats at 350 sq ft/gallon coverage, you'd need about 2.2 gallons of paint, typically rounded up to 3 gallons to have enough.
Should I subtract windows and doors from my paint calculation?
For most rooms, windows and doors take up a small enough percentage of wall area that many painters skip the deduction and treat it as a buffer for touch-ups and mistakes. If your room has large windows or multiple doors, subtracting 5-15% of the wall area gives a more accurate estimate.
How many gallons of paint cover 1000 square feet?
At a typical coverage rate of 350 sq ft per gallon, 1000 sq ft needs about 2.9 gallons for one coat. For two coats, that doubles to roughly 5.7 gallons of paint.
Does paint coverage rate vary by brand or paint type?
Yes, coverage rates typically range from 250 to 400 sq ft per gallon depending on the paint brand, sheen, and the surface being painted (textured or porous surfaces like drywall may need more paint than smooth, previously painted surfaces). Always check the coverage rate listed on your specific paint can.
Do I need primer in addition to paint?
If you're painting over bare drywall, a drastically different color, or a stain, you'll typically need a separate coat of primer, which is calculated the same way as one coat of paint using the primer's own coverage rate.

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About these results: Figures are for planning only. Confirm anything you will buy, bill, or submit (materials, payroll, medical screening) against the label, a quote, or a professional.