Commercial Paint Estimator

Those figures are standard trade-estimating deductions for a typical 3'x7' door and a mid-size window, used because most estimators don't have exact opening dimensions when quoting a job. If your project has oversized storefront glass or large double doors, the calculator will overstate the true paintable area — for a precise bid on jobs with unusual openings, measure them directly and adjust the wall area input downward yourself.

The engine always computes primer as a single pass over the paintable area regardless of the coats you enter for the topcoat, since most jobs only need one primer coat before multiple finish coats go on. If your surfaces need two coats of primer (bare drywall, stain-blocking, or a major color change), double the Primer Gallons figure manually before ordering.

Paint is sold by the can, so the calculator uses Math.ceil to round the raw division result up to the next full gallon — you can't buy 4.3 gallons, only 5. This means the tool always errs toward slightly more material than the bare math requires, which is the safer assumption for avoiding a mid-job store run.

Labor hours multiplies paintable area by your number of coats, then divides by 150 — a rule-of-thumb production rate of 150 sq ft covered per hour per coat with a roller. That rate assumes open wall and ceiling surfaces; it doesn't account for cut-in work around trim, multiple colors, ladder time on tall ceilings, or heavily textured surfaces, all of which slow a real crew down well below this planning figure.