About the Paint Calculator
Buying too little paint means an inconvenient mid-project store run and a potential color-batch mismatch; buying too much wastes money on unused cans. Getting the estimate right depends on accurately accounting for wall area, the openings that don't need paint, and how many coats the project requires.
This calculator computes total wall area from perimeter and height, subtracts standard estimated area for doors and windows, multiplies by your number of coats, and divides by a standard paint coverage rate of roughly 350 square feet per gallon — the typical coverage most interior paint brands specify on their labels.
Frequently Asked Questions
Why 350 square feet per gallon?
This is a commonly cited average coverage rate for interior wall paint, though actual coverage varies by paint brand, formula (flat vs. gloss), and wall texture — always check your specific paint can's label, which often lists exact coverage.
Do I need a different coat count for a color change?
Generally yes — going from a dark wall color to a much lighter one (or vice versa) often needs an extra coat or a tinted primer first, beyond the standard two coats assumed for most straightforward repaints.
Should I round up when buying paint cans?
Yes — it's standard practice to round up to the next full can and keep a little extra for touch-ups later, since matching a paint batch exactly months or years later can be difficult.