How many gallons of paint do I need for a 12x12 room?

A 12x12 room with 9ft ceilings, 1 door and 2 windows needs approximately 2 gallons of wall paint for two coats at 400 sq ft per gallon coverage. Add 1 quart for the ceiling if painting it separately.

Is it better to buy quarts or gallons of paint?

Buy quarts for areas under 100 square feet or for touch-ups. For anything larger, gallons are more economical — typically offering 4x the coverage at 2-3x the price of a quart.

How Many Gallons of Paint Do I Need?

Q: Do I need primer before painting?

You need primer when painting new drywall, switching from a dark to a light color, covering stains or water damage, or painting raw wood. For same-color touch-ups on previously painted walls in good condition, primer is optional.

Q: How much does a gallon of paint cover?

One gallon of paint covers 350-400 square feet on smooth primed surfaces. Rough, textured, or unprimed surfaces reduce coverage to 300-350 sq ft per gallon. Premium paints with higher pigment density may cover up to 450 sq ft per gallon.

Q: Should I calculate ceiling paint separately?

Yes. Ceiling paint is typically a flat sheen and a different product from wall paint. Calculate ceiling area as length x width and divide by your coverage rate. A standard 12x12 ceiling needs about 1 quart per coat.

Brand-neutral paint calculator with ceiling, primer, trim, and cans-to-buy output. Works for any paint brand.

⚡ Quick Answer

A 12×12 room with 9ft ceilings, 1 door, and 2 windows usually needs
about 2 gallons for 2 coats of wall paint at standard coverage.
Add about 1 quart for the ceiling. Need primer? Add
about 1 gallon.

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Common Paint Questions

How much does one gallon of paint cover?

Gallons Needed by Room Size

Wall paint only · 2 coats · 400 sq ft/gal · 1 door + 2 windows deducted

Room Size	Ceiling Height	1 Coat	2 Coats	Ceiling Add-On
8 × 10	8 ft	1 gal	1.5 gal	+ 1 qt
10 × 10	8 ft	1 gal	2 gal	+ 1 qt
12 × 12	9 ft	1.5 gal	2 gal	+ 1 qt
14 × 16	9 ft	2 gal	3 gal	+ 1 qt
20 × 20	9 ft	2.5 gal	5 gal	+ 1 gal

How This Calculator Compares

Brand calculators are often built around their own product specs. This one lets you adjust coverage for your actual surface.

Feature	Brand Calculators	FreeHomeCalc
Coverage rate	Often fixed	Adjustable 250–450 sq ft/gal
Doors & windows	Varies	Counted separately
Ceiling	Often separate	Built-in toggle
Primer	Usually guidance only	Calculated inline
Multiple rooms	Usually one room	Up to 4 rooms