Trim Paint Calculator
Trim paint comes in quarts for a reason — you rarely need a full gallon. Enter your room dimensions and which components you're painting. We'll size the quart count exactly.
Advanced options
- Baseboard linear ft
- 0
- Baseboard paint area
- 0 sq ft
- Door casings area
- 0 sq ft
- Window casings area
- 0 sq ft
- Door faces area
- 0 sq ft
- Total paintable
- 0 sq ft
- Gallon equivalent
- 0
- Estimated cost
- —
How the trim calculator works
Trim paint covers more surface area per gallon than wall paint because you're painting narrow strips, not broad walls — but the layout is fiddly. This calculator breaks the room into the four surfaces that typically get trim paint, adds them up, and rounds to whole quarts.
Baseboards: total perimeter of the room 2 × (length + width) times the baseboard's face width (default 3.5" for standard modern baseboards). Multiply by coats.
Door casings: approximately 17 linear feet per door (two sides at 6'8" + top at 3' + margin). At a 2.5" casing profile, that's ~3.5 sq ft per door per coat.
Window casings: approximately 14 linear feet per standard window. At a 2.25" casing, that's ~2.6 sq ft per window per coat.
Door faces: a standard 3' × 6'8" door is about 20 sq ft per side — 40 sq ft per door per coat if you paint both sides. This is by far the biggest area contributor if you include it.
When to uncheck components
- Skip door faces if your doors are hollow-core factory-finished or stained wood you're leaving as-is. Cuts paint needs by more than half.
- Skip window casings if your windows are newer vinyl units with integrated trim that doesn't get painted.
- Skip door casings on interior openings without actual doors (cased openings are rare but exist).
- Skip baseboards only if you've already painted them recently and just want a touch-up — in which case a sample-size pint is enough.
Why semi-gloss for trim
Every component here gets touched, bumped, cleaned, or scuffed more than walls. Semi-gloss paint is denser than flat/eggshell paint, which means it resists scuff marks, wipes clean without the paint "flashing" (showing a wet spot), and gives crisper lines at the inside corners where trim meets wall. Gloss is even more durable but shows every imperfection and brush stroke — most pros pick semi-gloss.
Common questions
Why quarts instead of gallons?
Unless you're trimming a whole house at once, quarts (1/4 gallon) is usually enough and avoids storing leftover paint. A 1-gallon can of trim paint can do roughly 3–5 rooms, depending on what you include. If the calc says ≥4 quarts, buying the gallon is cheaper.
Do I need primer under trim paint?
For already-painted trim in good condition, no. For bare wood or stained/glossy surfaces, yes — or use a self-priming trim paint (most modern ones are). Primer coverage is similar to paint; add 1 extra quart per 3 rooms if you need it.
Can I use wall paint on trim?
Technically yes, but you'll regret it. Wall paints at flat or eggshell finish mark up and don't clean well. The extra few dollars for actual trim paint pays off every time a kid runs a sticky hand across the baseboard.
What about crown molding or chair rails?
Not included in the default math. Rough rule: add 20–30% to the baseboard estimate if your room has a matching crown profile, or 10–15% for a chair rail. We'll probably add explicit toggles for these in a v1.
For the walls, ceiling, and overall room paint estimate, head to the paint calculator.