Interior wall paint
Interior Paint Calculator USA 2026
Paintable area = wall perimeter × ceiling height − doors and windows, divided by 350 ft² coverage per gallon, multiplied by the number of coats.
Reviewed by BuildMate Editorial Team Construction Researchers Updated March 2026 2 min read Fact-checked
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Paintable wall area366 sq ft
Gallons required2.1 gal
Quart cans (if <1 gal)9
Show calculation steps
- Gross wall area = 52 × 8 = 416 sq ft
- Openings = 1×20 + 2×15 = 50 sq ft
- Paintable area = 416 − 50 = 366 sq ft
- Gallons = (366 × 2) ÷ 350 = 2.09 gal
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How the interior wall paint math works
Paintable area = wall perimeter × ceiling height − doors and windows, divided by 350 ft² coverage per gallon, multiplied by the number of coats.
Gallons = (Wall Area − Openings) × Coats ÷ 350 sq ft per gallon
Frequently asked questions
How much does a gallon cover?
Roughly 350 sq ft on primed drywall.
Do I need primer?
Yes on new drywall or drastic color changes.
Estimates based on 2026 RSMeans USA data and national material averages. Always confirm quantities with your supplier or contractor before ordering.