It also handles primer, multiple coats and the cost. Use it before you head to the hardware store so you buy the right number of gallons in one trip. For paint used on trim, cabinets or textured finishes, set the coverage rate lower (around 250 sq ft per gallon) to be safe.
Calculator
Formula used
Paintable area = walls − doors − windows · Gallons = area × coats ÷ coverage
How to use the Paint Coverage Calculator
- Measure each wall (length × height) and add them up.
- Subtract the rough area of doors (about 21 sq ft each) and windows (about 15 sq ft each).
- Choose the number of coats and the coverage rate from the paint can.
- Add the price per gallon to get a cost estimate.
About this tool
The Paint Coverage Calculator is built for speed and accuracy: every calculation runs in your browser, so your data never leaves your device and the result updates as you type. It works equally well on a phone, a tablet or a desktop, and it is free to use as many times as you like.
Common use cases
- Planning a single-room refresh.
- Quoting a whole-house repaint.
- Comparing two paint prices per gallon.
- Working out primer for new drywall.
Tips for the best result
- Use the latest figures you have - even a small change in rate or term can shift the outcome by hundreds.
- For annual figures, divide by 12 to get a monthly number you can compare with the result.
- Bookmark this page and revisit the calculation as the inputs change.
Frequently asked questions
How accurate is this estimate?
Within about 10% if your measurements and coverage rate are right. Buy a little extra for touch-ups and porous surfaces.
What coverage should I use?
Premium interior latex covers about 350-400 sq ft per gallon on smooth drywall; cheaper paints and exterior masonry need 250-300.
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