Paint Calculator
Work out gallons of paint for a room from wall dimensions, doors, windows, and coats — with a buy-this-many answer.
Processed locally in your browser — nothing is uploaded.
Walls
Deducted at 21 sq ft each
Deducted at 15 sq ft each
Typical paint covers ~350 sq ft per gallon per coat
Results
- Wall area
- 352 sq ft
- Paintable area
- 301 sq ft
- Area to cover (all coats)
- 602 sq ft
- Paint needed
- 1.72 gal
- Buy
- 2 gal
After door and window deductions
Or 7 quarts for small jobs
Estimate assumes smooth, primed walls. Porous or dark surfaces may need more paint.
About Paint Calculator
Add each wall as length × height, tell it how many doors and windows to subtract, and pick your coat count. The calculator totals the paintable area, divides by the coverage rate, and rounds up to whole gallons (or quarts for touch-up jobs).
Doors are deducted at 21 sq ft and windows at 15 sq ft — the standard estimating shortcuts — and coverage defaults to 350 sq ft per gallon, the figure most paint brands print on the can.
Common uses
- Buy the right number of gallons for a bedroom repaint in one trip
- Compare paint needed for one coat vs two
- Estimate paint for a whole floor by adding every wall
Example
Input
Two 12×8 ft + two 10×8 ft walls, 1 door, 2 windows, 2 coats
Output
301 sq ft paintable → 1.72 gal exact → buy 2 gallons
Limitations
- Assumes smooth, primed surfaces; textured, porous, or dark walls need extra paint
- Door/window deductions use flat 21 and 15 sq ft estimating figures
- Ceilings and trim are not included — run them as separate calculations