Wall Paint Quantity Calculator Calculate total paint required in Liters and Gallons for room walls. Room Length (Feet) Room Width (Feet) Wall Height (Feet) Number of Coats 1 Coat 2 Coats (Recommended) 3 Coats Number of Doors (Standard 20 Sq Ft) Number of Windows (Standard 15 Sq Ft) Calculate Required Paint Calculating Wall Area & Paint Volume… 0% Paint Needed — In Gallons — Paintable Area — Vote