Short answer
For an 8x10 bathroom with 8-foot ceilings, 1 door, 1 window, and 2 coats of paint, you need 1.44 gallons of wall paint. Add a quart for the ceiling and 2 quarts for trim. If you're buying in gallons, two 1-gallon cans covers the walls with a little left for touch-ups.
How this calculator works
The core question—how much paint for an 8x10 bathroom—comes down to paintable wall area divided by coverage rate, multiplied by the number of coats.
Step 1: Calculate gross wall area
The four walls of a rectangular room form a perimeter. Multiply that perimeter by ceiling height to get total wall area:
2 × (length + width) × height 2 × (8 + 10) × 8 = 288 sq ft
Step 2: Subtract doors and windows
You don't paint over doors and windows, so the calculator removes them from the wall area. Each standard interior door is estimated at 21 sq ft (roughly 3 ft × 7 ft). Each window is 15 sq ft (roughly 3 ft × 5 ft). For 1 door and 1 window:
288 − (1 × 21) − (1 × 15) = 252 sq ft of paintable wall area
Step 3: Multiply by coats
Two coats means you're covering that surface twice:
252 × 2 = 504 sq ft total coverage needed
Step 4: Divide by coverage rate
The formula uses 350 sq ft per gallon, which reflects real-world application on smooth, previously painted or primed drywall. Manufacturer labels often say 400 sq ft/gallon, but that's a lab test on perfectly flat surfaces. In practice, rollers don't lay paint in a perfectly uniform film, and texture, nap depth, and lap zones eat into that number.
504 ÷ 350 = 1.44 gallons
Secondary outputs
The calculator also produces three supporting figures:
- Ceiling paint (0.23 gallons, 1 coat): The ceiling is simply length × width ÷ 350. At 80 sq ft, one coat needs less than a quart. Buy a quart and call it done.
- Quart cans (6 quarts): If you prefer quarts, the 1.44-gallon total rounds up to 6 quarts. Quarts work well when you want to test a color or when a gallon would leave too much paint to store.
- Trim/door paint (2 quarts): Trim gets its own calculation—doors and windows multiplied by 0.25 quarts each, plus a base quart for baseboard and any other millwork. For 1 door and 1 window, that's 2 quarts.
What the calculator does not account for
The formula does not add a waste factor. Spills, roller splatter, and learning-curve waste on the first wall can run 5–10%. For most homeowners, the rounding from 1.44 gallons to 2 gallons already absorbs that buffer. If you're mixing a custom color, buy slightly more than you think you need—color-matching a dried sample after the fact is inexact.
The coverage rate also assumes smooth, sealed surfaces. Textured walls—orange peel, knockdown, or skip trowel—can drop to 300 sq ft/gallon or lower. If your bathroom has heavy texture, recalculate at 300 sq ft/gallon, which would push wall paint to about 1.68 gallons for the same room.
Finally, going from a very dark existing wall color to a lighter one (or vice versa) almost always requires a tinted primer plus two topcoats. The calculator handles the topcoat math; budget a separate quart of primer.
Recommended materials
For an 8x10 bathroom, you'll work through paint quickly because of the tight quarters—a good roller and reliable tape matter more here than in a large room where you have room to maneuver. On the paint side, a satin or semi-gloss formula holds up against shower steam and wipes clean. For tools, a 9-inch roller moves faster than a 4-inch touch-up roller on open walls, and sharp masking tape keeps trim lines clean where the wall meets tile or cabinetry.
- Behr Premium Plus interior paint (1 gallon) — available in satin and semi-gloss finishes suited to bathroom humidity
- Purdy 9-inch roller cover (3-pack) — a 3/8-inch nap works on smooth-to-light-texture walls; swap covers between wall color and ceiling to avoid cross-contamination
- Frog Tape painter's masking tape (1.41-inch x 60yd) — the paint-block adhesive seals tape edges against bleed, which is especially useful along tile lines
FAQ
How many gallons of paint do I need for an 8x10 bathroom? With 8-foot ceilings, 1 door, 1 window, and 2 coats, you need 1.44 gallons of wall paint. Buying two 1-gallon cans is the most practical option, and any leftover makes a good touch-up supply.
Can I buy quarts instead of gallons for a small bathroom? Yes. The 1.44-gallon total converts to 6 quart cans. Quarts cost more per ounce but let you try a color without committing to a full gallon, which makes sense for a small bathroom.
How much ceiling paint does an 8x10 bathroom need? An 8x10 ceiling is 80 square feet, which works out to about 0.23 gallons for one coat—well under a quart. Most painters use a quart of ceiling paint and have some left over.
How much trim and door paint do I need? For 1 door and 1 window, plan on 2 quarts of trim paint. That covers both surfaces with standard semi-gloss and gives you enough to do a second coat if needed.
What coverage rate does this calculator use? The formula uses 350 square feet per gallon, which is a real-world figure for smooth, primed drywall. Rough or unprimed surfaces absorb more paint and may drop coverage to 300 sq ft/gallon or less.
Does the calculator include a waste factor? No built-in waste factor is added to the 1.44-gallon figure—the formula accounts for door and window deductions but not spills or touch-ups. Adding 10% gives you about 1.6 gallons, which rounds up to 2 gallons anyway.
Do I need to prime a bathroom before painting? If you're painting over bare drywall, a dark color, or water-stained walls, yes—prime first. Primer is calculated separately; a quart typically covers one coat on a small bathroom.
Should I use a different paint finish for bathrooms? Satin or semi-gloss finishes are standard for bathrooms because they resist moisture and wipe clean. Flat paint absorbs humidity and shows scuffs quickly in wet areas.
How does ceiling height affect paint quantity? Every extra foot of ceiling height adds 2 × (length + width) square feet of wall area—36 sq ft in an 8x10 room. At 9-foot ceilings, you'd need about 1.65 gallons instead of 1.44.
Can I get away with one coat of paint in a bathroom? One coat works only if you're applying the same color over an identical existing color in good condition. Going from white to a saturated color, or repainting after moisture damage, always needs two coats.