Wall area math

Wall area = perimeter × height, minus openings. A 5×8 bathroom with an 8-foot ceiling: 2 × (5 + 8) × 8 = 208 sq ft, minus a door (~21 sq ft) and window (~12 sq ft) ≈ 175 sq ft. Then skip tile you're keeping.

Skip the tile

Bathrooms have tub surrounds and backsplashes that stay tiled. A 3×5 tub surround is about 30–40 sq ft of wall you won't paint — subtract it from the wall total. That drops the 5×8 example to about 160 sq ft.

The ceiling is separate

The ceiling takes its own paint — length × width for a 5×8 is about 40 sq ft, under a quart of ceiling paint. Use flat white or a mold-resistant ceiling formulation; don't reuse wall paint up there, it sheens oddly under bathroom lighting.

Finish: satin or eggshell

Satin or eggshell on walls — both resist moisture and wipe clean better than flat. Ceiling: flat or matte. In humid bathrooms, use a formulation with mildewcide; it's the single best defense against pink mold on caulk lines and corners.

Primer and mold resistance

Prime bare drywall and any patched areas — one coat seals and evens absorption. Use a stain-blocking primer over water stains. On previously painted walls in good shape, paint can go straight on. Two coats of paint are standard for even color.

Worked example: a 5×8 bathroom

• Wall area = 208 − door − window − tub surround ≈ 160 sq ft
• ÷ 350 sq ft/gal ≈ 0.46 gal per coat
• Two coats → ~1 gallon of wall paint
• Ceiling 40 sq ft → 1 quart

FAQ