Paint Calculator
Find out how much paint you need for your room. Enter your wall dimensions, doors, windows and number of coats to get an instant estimate in gallons and liters.
Result
Enter your numbers to see the estimate.
How this calculator works
Buying the right amount of paint saves you an extra trip to the store and avoids paying for cans you don't need. This paint calculator estimates the paintable area of your room by taking the total wall area and subtracting standard allowances for doors and windows, then dividing by your paint's coverage rate to get gallons and liters needed.
Most interior paints cover between 250 and 400 square feet per gallon on a smooth, primed wall, with 350 sq ft/gallon being a common average. Textured walls, unprimed drywall and darker color changes typically need more paint and an extra coat. If you're painting over a dramatically different color (like white over dark red), plan for at least two coats regardless of what the can says.
Standard door openings are estimated at about 21 sq ft (3 ft × 7 ft) and windows at about 15 sq ft (3 ft × 5 ft) — enough to account for trim without over-subtracting. If your doors or windows are unusually large or small, adjust your final estimate accordingly. Use the "Include ceiling" option if you're painting the ceiling in the same color, which adds the floor area to your total.
Example: A 12 ft × 10 ft room with 9 ft walls, 1 door, 2 windows and 2 coats needs roughly 2 gallons (about 7.5 liters) of paint, based on 350 sq ft of coverage per gallon.
How it works
Enter your measurements or costs
Fill in the room size, materials or costs for your project. No sign-up required.
Adjust the settings
Choose your units, waste percentage and any project-specific options.
Get your estimate instantly
See your results calculated instantly, right in your browser.
Frequently asked questions
How much paint do I need for a 12x12 room?
For a 12 ft × 12 ft room with 8 ft walls, two doors and one window, painted with two coats, you'd need roughly 2 gallons of paint, assuming 350 sq ft of coverage per gallon. Use the calculator above with your exact measurements for a precise estimate.
How many coats of paint do I need?
Two coats is standard for most projects, especially when changing colors or painting over a darker shade. A single coat may be enough when refreshing a wall with the same color.
Does paint coverage vary by brand?
Yes. Coverage is usually printed on the paint can, typically between 250-400 sq ft per gallon. Use your specific product's coverage rate in the calculator for the most accurate result.
Should I subtract doors and windows from wall area?
Yes, this calculator automatically subtracts a standard area for each door and window you enter, since you don't paint over them.
How accurate are these calculators?
This calculator gives a solid estimate based on standard assumptions. Actual paint requirements may vary depending on surface texture, paint type, coverage and application method — buy a little extra or keep your receipt for an easy exchange.