Assumptions used: 350 sq ft coverage per gallon per coat (check your specific paint can — varies 250-400 sq ft/gallon by brand) · 20 sq ft deducted per door, 15 sq ft per window · 10% waste factor added · trim estimated at 450 linear ft per gallon · all gallon amounts round up to the nearest whole can. This is a planning estimate, not a guarantee — actual usage varies by wall texture, paint type, and application method.