Paint estimator
The fastest way to underestimate paint is to forget that **coats multiply everything**. One room that “needs about a gallon” becomes 2–3 gallons the moment you do two coats, plus ceiling, plus primer, plus “oops, that wall is thirsty.” Paint math is simple — the workflow isn’t.
For developers: API access
Same result via GET request (use current inputs above):
curl -s "https://howdeedo.com/api/calc/paint-estimator?areaSqFt=400&coats=2&coverageSqFtPerGallon=350"fetch("https://howdeedo.com/api/calc/paint-estimator?areaSqFt=400&coats=2&coverageSqFtPerGallon=350").then(r => r.json())Get an API key for higher limits and stable access.
Good to know
Dark-to-light is the budget trap. Switching from a saturated color to a light neutral often needs extra coats (or primer) because you’re fighting the old color showing through. That’s not “bad paint,” it’s physics: you’re trying to block light.
Ceilings drink paint differently. Flat ceiling paint and textured ceilings tend to use more paint per square foot than smooth walls. If your ceiling has texture, plan for lower coverage — and a little extra patience.
Openings are smaller than you think. People often subtract “a whole wall” for windows and doors, but a standard door is only ~20 sq ft. A couple windows might be another ~30–40. Unless you’re in a glass house, openings usually don’t cut your paint by half.
Methodology, disclaimers & sources
How it works
- Compute paintable area: walls (perimeter × height) minus openings + optional ceiling.
- Multiply by number of coats (and primer if enabled).
- Divide by coverage (sq ft per gallon), then add waste if enabled.
Details & assumptions
Default coverage is based on common manufacturer ranges for typical interior/exterior paints. Surface condition and technique can change real coverage significantly. This is an estimate for planning and purchasing — not a guarantee.