Estimate a paint job by production rate

Because paint cost is the small part — labor is where painters make or lose money. A production rate is how fast you cover a surface: walls roll fast (150–200 sq ft an hour per coat), ceilings are slower, and trim and doors are slow detail work measured differently. Adding one flat "per square foot" number hides all of that. Estimating each surface at its own rate is how the accurate quotes get built.

One gallon covers about 350 square feet in one coat. Multiply your wall and ceiling area by the number of coats, divide by 350, and round up. This calculator does it automatically for the surfaces measured in square feet (trim and doors are counted in labor, not wall-paint gallons).

Rough starting points per coat: walls 150–200 sq ft/hour, ceilings 100–150 sq ft/hour, trim and baseboard 50–70 linear ft/hour, and about one hour per door including both sides and edges. Rougher surfaces, heavy prep, and cutting-in all slow these down — so tune the rates to your own crew.

Interior repaints commonly land around $2 to $6 per square foot of floor area once walls, ceilings, trim, prep, and materials are included — but that's an outcome of the labor and materials math, not an input. Estimate the hours and gallons first; the per-square-foot figure falls out of it.

Add your labor (hours times your hourly rate) to materials (gallons times price per gallon), then apply your markup for overhead and profit. This calculator shows that total, plus the hours and gallons behind it.