How Much Paint Do I Need for Trim and Doors?
Quick answer: linear feet of trim × width gives area — add ~20 sq ft per door and ~15 sq ft per window, divide by 350–400 sq ft per gallon. A typical 3-bedroom house needs about 1 gallon of trim paint for two coats.
- The trim formula
- Doors and windows
- Sheen for trim
- Worked example: 3-bedroom house
- Common mistakes
- FAQ
The trim formula
Trim is usually quoted in linear feet, not square feet. Convert it: linear feet × width in inches ÷ 12 = trim area. Baseboard in a 12×12 room is about 44 linear feet; at 4 inches wide that's 44 × 4 ÷ 12 ≈ 15 sq ft. Add door and window casing the same way. Coverage stays the standard 350–400 sq ft per gallon.
Doors and windows
Count each interior door as about 20 sq ft per face (a 3×7 ft door is 21 sq ft) — paint both faces and the frame if you're matching trim, one face if only the room side. Count each window as about 15 sq ft of casing and sash. A 3-bedroom house with ~6 doors and ~8 windows adds roughly 240 sq ft of door + window area to the trim total.
Sheen for trim
Use semi-gloss or satin on trim and doors. The higher sheen is washable, stands up to fingerprints, and makes the trim read against flat walls. Flat paint on trim picks up marks and is hard to clean — a common DIY mistake. The same gallon of semi-gloss covers the same 350–400 sq ft.
Worked example: a 3-bedroom house
- Baseboards: ~180 linear ft × 4 in ÷ 12 = 60 sq ft
- Casing: ~120 linear ft × 3 in ÷ 12 = 30 sq ft
- 6 doors × 20 sq ft = 120 sq ft
- 8 windows × 15 sq ft = 120 sq ft
- Total ≈ 330 sq ft → 1 gallon per coat, 2 gallons for two coats (or 1 gallon if painting one coat)
Common mistakes
- Ignoring trim in the wall estimate. If you're painting walls AND trim, measure trim separately — it needs a different sheen and its own gallon.
- Using flat paint on trim. It fingerprints and doesn't clean up. Semi-gloss or satin only.
- Forgetting door edges. The edge of a door is visible when it's open and gets painted too — it's part of the 20 sq ft per face.
- Under-counting tall rooms. High ceilings add casing above windows and sometimes crown molding — count every linear foot you'll actually paint.
FAQ
Multiply trim linear feet by its width in inches ÷ 12 for area, add about 20 sq ft per door and 15 sq ft per window, then divide by 350–400 sq ft per gallon. A typical 3-bedroom house needs about 1 gallon of trim paint for two coats.
Count baseboards and casing by linear feet (length × width ÷ 12 for area), count each door as about 20 sq ft, each window as about 15 sq ft, add them, and divide by coverage. Round up to the nearest gallon.
About 350–400 sq ft per gallon per coat — the same coverage as wall paint. With two coats, one gallon covers roughly 175–200 sq ft of trim in practice.
Yes — count both faces of an interior door, about 20 sq ft each side, or 40 sq ft per door total. Many people paint the room-side face only when matching trim, which cuts the count to one face.
Use semi-gloss or satin for trim and doors — the higher sheen is washable, stands up to fingerprints, and makes trim pop against flat walls. Flat paint on trim picks up marks.