Exterior paint calculator
Estimate exterior paint for siding, trim, garage doors, and shutters. Use the wall-area or square-footage entry below; the calculator returns gallons and a Kompozit shopping plan.
Estimates round up to the nearest quart and are based on Kompozit's published coverage. Buy slightly more for touch-ups and color changes.
Exterior coverage runs lower than interior
Two reasons. First, exterior surfaces are usually more textured (lap siding, stucco, T-111), which sucks paint into the profile. Second, exterior paints are formulated with more flexible, UV-stable resins that lay down a slightly thicker film on purpose. Plan for ~350 sq ft per gallon, or less on rough stucco.
Why two coats outside, almost always
Sun, rain, and freeze/thaw will eat any film thinner than two full coats. The 15-year warranty on Kompozit PRO is two coats. Big-box premium paints rated for 25-year exterior life are also two coats. Don't skip.
Trim, doors, garage doors, shutters
Subtract their area from the wall total — this calculator does that automatically. We use 21 sq ft for a standard door, 112 sq ft for a double garage door, 15 sq ft per window, and 12 sq ft per pair of shutters. Then if you're painting trim a different color, tick the trim checkbox to add ~10% paint volume in the trim color.
FAQ
Walk the perimeter, multiply by height. A 40' × 30' two-story house: perimeter = 140 ft, height = 18 ft (two 9-ft stories), wall area ≈ 2,520 sq ft. Use a preset if you don't want to measure.
Yes if siding is bare wood, badly weathered, or chalking. Use Kompozit PRIME first. PRO and ONE are paint-and-primer-in-one for previously painted surfaces in good condition.
Both eat more paint than smooth siding. For stucco, add 25% to the gallons. For brick, plan for 200 sq ft/gal — heavy texture really matters.