Paint Calculator

Gallons of paint for a room from wall dimensions, doors, windows and coat count.

ft

Or total wall length.

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Enter your details and press Calculate to see results.

Formula

gallons = paintable area × coats ÷ 400 sq ft per gallon

Example

A 12×12 room with 8 ft ceilings: ~368 sq ft walls − 42 sq ft openings ≈ 326 sq ft → about 1.7 gallons for two coats; buy two gallons.

Buying smart

Paint rounds up to whole cans anyway, so buy the calculated amount rounded up and keep leftover for touch-ups. Dark colors over light walls often need tinted primer to avoid a third coat.

Frequently asked questions

How much wall does one gallon cover?

Typically 350–400 sq ft per coat for quality paint on primed drywall; porous or textured surfaces reduce this.

Does this include the ceiling?

No — add ceiling area separately at one coat if you're painting it too.

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