How much area does one gallon of paint cover?

One gallon of interior latex paint covers approximately 350 square feet on smooth, primed drywall in a single coat. This is the industry-standard rate published by Sherwin-Williams, Benjamin Moore, and Behr, based on ASTM D5150 spread rate testing. Textured surfaces reduce coverage to 280-300 sq ft per gallon.

How many gallons for a 12x12 room?

A 12x12 ft room with 8 ft ceilings has 384 sq ft of wall area. Subtract 1 door (21 sq ft) and 2 windows (30 sq ft) for 333 sq ft of paintable area. At 2 coats, that is 666 sq ft divided by 350 sq ft/gallon = 2 gallons needed.

How do I calculate paint needed?

Calculate wall area using 2 x (length + width) x ceiling height. Subtract 21 sq ft per door and 15 sq ft per window. Multiply by number of coats (usually 2). Divide total by 350 sq ft per gallon and round up to the nearest whole gallon.

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Paint Calculator

Calculate exactly how many gallons of paint you need. Enter room dimensions (length, width, and ceiling height), subtract doors and windows, and get coverage based on the industry-standard rate of 350 sq ft per gallon for interior latex paint. Works for any brand — Sherwin-Williams, Benjamin Moore, Behr, and more.

Room Dimensions

Length (ft)

Width (ft)

Ceiling Height (ft)

Number of Coats

Doors

Windows

Enter room length and width to see your estimate.

Next Steps After Calculating

Once you know how much paint to buy, use these free Paint Color HQ tools to finalize your project:

Preview your color — open the Room Visualizer to see your chosen shade on walls before purchasing.
Compare shades side by side — the Color Comparison tool shows colors from Sherwin-Williams, Benjamin Moore, Behr, Valspar, PPG, Dunn-Edwards, and Farrow & Ball next to each other with Delta E difference scores.
Choose the right finish — read our paint sheen guide covering flat, eggshell, satin, semi-gloss, and high-gloss — with recommendations by room type.
Build a full palette — use the Palette Generator to create coordinating color schemes for your entire home.

Paint Calculator

Room Dimensions

Next Steps After Calculating

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