Paint Calculator — ft, sq ft, gallons & cost
How to use this calculator
Choose a surface mode — room walls, ceiling, single wall, or custom area. Enter dimensions in feet and inches, select paint type and number of coats. Doors and windows are automatically deducted. Results update instantly.
Paint types — Flat/Matte (400 ft²/gal), Eggshell (350), Satin (350), Semi-Gloss (350), Gloss (300).
Primer — 1 coat at 300 ft²/gal for new drywall, dark-to-light color changes, or stain blocking.
Cost — price per gallon of paint and primer, plus optional flat-rate for supplies (rollers, brushes, tape, drop cloths).
Saved Calculations
| Time | Mode | Area ft² | Paint gal | Primer gal | Coats | Total $ |
|---|
How to Calculate Paint for a Room
This paint calculator estimates the gallons of paint and primer needed for walls, ceilings, or any custom surface area. Enter room dimensions in feet and inches, choose your paint finish (flat, eggshell, satin, semi-gloss, or gloss), select the number of coats, and optionally add primer. Doors (21 ft² each) and windows (12 ft² each) are automatically subtracted.
Formulas Used
Paintable area = wall perimeter × height − doors − windows.
Paint gallons = ceil(paintable area × coats × (1 + waste%) ÷ coverage per gallon).
Primer gallons = ceil(paintable area × (1 + waste%) ÷ 300).
Paint Coverage by Finish
Flat/Matte: 400 ft²/gal — best for ceilings and low-traffic areas. Eggshell: 350 ft²/gal — most popular for living rooms and bedrooms. Satin: 350 ft²/gal — kitchens, bathrooms, hallways. Semi-Gloss: 350 ft²/gal — trim, doors, cabinets. Gloss: 300 ft²/gal — high-moisture areas and accent surfaces.
FAQ
Do I need primer? Yes, if painting new drywall, going from dark to light colors, or covering stains. One coat of primer at 300 ft²/gal is sufficient for most situations.
