Bathrooms are the one room where standard interior paint is a recipe for mold. The constant humidity from showers, baths, and running water creates an environment where regular latex paint breaks down within 6 to 12 months, developing mildew spots and peeling edges near the shower. Moisture-resistant paint with built-in mildewcide is not optional here.
The good news: bathrooms are small. A standard 8x10 bathroom has about 230 square feet of wall area after subtracting the door, window, and vanity mirror. At two coats, you need about 1.5 gallons. Even with premium moisture-resistant paint at $50 per gallon, the total paint cost for a bathroom is under $80.
The finish you choose matters as much as the paint type. Semi-gloss is the traditional bathroom choice because water beads on its surface and it wipes clean easily. Satin is a viable alternative if you want slightly less sheen. Never use flat or matte paint in a bathroom, regardless of what the marketing says about "washable matte" formulations. Moisture will find the weak points.
A standard 8x10 bathroom needs 1.5 to 2 gallons of moisture-resistant paint for two coats, using satin or semi-gloss finish.
Bathroom paint calculations follow the standard area formula with a few adjustments. Wall area equals perimeter times height, minus the door (21 sqft), window if present (15 sqft), and vanity mirror (typically 8 to 12 sqft). Most bathrooms also have a section of wall behind the shower or tub that is covered by tile or a surround panel, which should be subtracted.
A standard tub/shower surround covers approximately 40 to 50 square feet of wall area (the back wall and two side walls inside the tub enclosure). Subtract this from your paintable area since it will not be painted. The remaining walls around the vanity, toilet, and entry are your actual paintable surface.
Coverage rate for bathroom paint is similar to standard paint at 350 square feet per gallon. Two coats are always recommended for bathrooms, both for appearance and for building up the moisture-resistant barrier that protects the underlying drywall.
Use this calculator when refreshing a bathroom before guests visit, preparing a home for sale (clean, freshly painted bathrooms consistently rank among the top 3 features buyers notice), or addressing visible mildew that has penetrated the existing paint layer. If your bathroom paint is peeling near the shower, the issue is usually inadequate ventilation combined with non-bathroom paint. The fix is proper paint, not just another coat over the problem.