Paint Calculator

Estimate gallons for walls or a whole room. Enter total wall area, or room L×W×H with door and window deductions — coats, coverage, and waste included.

Inputs

Total wall area

sq ft

Sum of all surfaces you plan to paint (walls only, or walls + ceiling).

Coats

Default 2 coats for most interior jobs.

Coverage

sq ft/gal

Check the can — often 250–400 sq ft per gallon per coat.

Waste factor

Default 10% for touch-ups and absorption.

Results

—gallons

Paintable area —

With coats + waste —

Exact gallons —

Quarts (est.) —

Assumptions: Gallons are rounded up to whole cans. Quarts ≈ exact gallons × 4 (rounded up). Room mode deducts ~20 sq ft/door and ~15 sq ft/window. Always confirm coverage on the paint label.

Paint calculator FAQ

How much paint do I need for a room?

Get wall area (or use L×W×H with door/window deductions), multiply by coats, add waste, then divide by coverage (often ~350 sq ft per gallon).

How many square feet does a gallon of paint cover?

Many interior paints claim about 250–400 sq ft per gallon per coat. Default here is 350 — adjust to match your can.

Should I buy extra paint for waste?

Yes. A 5–10% buffer covers touch-ups and absorption. This tool defaults to 10%.

How big are typical doors and windows for paint math?

Room mode deducts about 20 sq ft per door and 15 sq ft per window. Change counts if your openings differ.

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Step-by-step guide: How many gallons of paint do I need? — formula, worked examples, and common mistakes.