Paint Sheen Guide: Flat to High Gloss
Paint sheen physics: flat to high-gloss on specular vs diffuse reflection, PVC chemistry, ASTM D2486 scrub ratings, and application techniques.
Read the guide →Paint Calculator
Estimate how many gallons of paint you need for any room, including walls and ceiling.
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How This Calculator Works
This paint calculator estimates how many gallons of paint and primer you need for walls, ceilings, and trim based on room dimensions and the number of coats.
How it works:
- Wall area: Room perimeter × wall height, minus door (21 sq ft each) and window (15 sq ft each) openings.
- Coverage: One gallon of premium paint covers approximately 350-400 sq ft per coat on smooth, primed drywall. Rough textures (knockdown, orange peel) reduce coverage to 250-300 sq ft per gallon.
- Number of coats: For most color changes, two coats of paint over a sealed primer coat gives the best sheen uniformity and scrub resistance.
Example: A 12×14 ft bedroom with 8-ft ceilings has roughly 416 sq ft of wall area minus 2 windows and 1 door = ~365 sq ft. Two coats = 730 sq ft → about 2 gallons of paint. See our paint sheen guide for choosing between flat, eggshell, satin, and semi-gloss.
Helpful Paint Calculator Resources
Paint Primer: When You Need It and When You Don't
When primer is required: Young's Equation for adhesion, stain blocking chemistry, paint-and-primer-in-one limitations, and substrate-specific primer selection.
Read the guide →Top Paint Brands Compared: What Pros Recommend
Sherwin-Williams vs Benjamin Moore vs Behr vs PPG compared on solids by volume, TiO₂ refractive index, KU/ICI rheology, and ASTM scrub ratings.
Read the guide →