Paint Calculator
Ready to give your living room a fresh color? Our free Paint Calculator removes the guesswork, telling you exactly how many gallons of paint you need to buy to cover your walls flawlessly.
Paint Calculator
What is the Paint Calculator - How Much Paint Do I Need??
The Paint Calculator is an interior design and DIY estimation tool. It calculates the total surface area of a room's walls, subtracts the areas that won't be painted (doors and windows), and divides the remainder by standard paint coverage rates.
How to use the Paint Calculator - How Much Paint Do I Need?
- Enter the total length of all the walls in the room.
- Enter the height of the walls from floor to ceiling.
- Input the number of standard doors and windows in the room to subtract their area.
- The tool outputs the exact number of gallons needed for one or two coats.
Example
A 12x12 room with 8-foot ceilings has a gross area of 384 sq ft. Subtracting one door (21) and one window (15) leaves a net area of 348 sq ft. 348 / 350 = ~1 gallon. For two coats, you need 2 gallons.
Understanding Your Results
The output tells you exactly what to ask for at the paint counter. Buying the right amount ensures the paint color is mixed from the exact same batch, avoiding subtle color discrepancies on your walls.
Common Use Cases
- Home Renovation: Calculating the gallons needed to paint an entire master bedroom suite, including the ceiling and trim.
- Contractor Bidding: A professional painter generating an accurate material cost estimate for a client's quote.
- Exterior Painting: Estimating the massive amount of paint required to coat the exterior siding of a two-story house.
How it Works
The tool multiplies Wall Length by Wall Height to get the gross square footage. It then subtracts 21 sq ft for every door and 15 sq ft for every window. Finally, it divides the net square footage by 350 (the industry standard coverage of one gallon of paint).
Tips & Accuracy Notes
- •Most high-quality paints require two coats for a perfect finish, regardless of what the 'one-coat guarantee' label says. Always plan for two coats.
- •If you are painting over a very dark color with a very light color, you may need to factor in a coat of primer before your two coats of paint.
Frequently Asked Questions
How much does one gallon of paint cover?
As a general industry rule of thumb, one gallon of premium interior acrylic latex paint covers between 350 to 400 square feet.
Do I need to calculate the ceiling separately?
Yes. Ceilings use 'flat' paint to hide imperfections, while walls usually use 'eggshell' or 'satin' paint for washability. Treat the ceiling as a completely separate calculation.
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Disclaimer: Tool assumes standard door (21 sq ft) and window (15 sq ft) sizes. Highly textured walls or bare drywall will absorb more paint and reduce the coverage per gallon.