How the Paint Calculator Works
The calculator multiplies wall width by height and wall count, subtracts the total door and window area, and multiplies the net area by the number of coats. It then divides by the coverage rate and adds the selected allowance.
Formula and method
Net wall area = (width × height × wall count) − openings. Paint quantity = net area × coats × (1 + allowance percentage) ÷ coverage per container.
Tips for better estimates
Use the coverage rate printed on the paint can. Enter the combined area of openings in the same square unit as the wall dimensions, and include a realistic allowance for touch-ups.
Important limitations
Coverage changes with surface texture, porosity, primer, application method, and color. This is an estimate; confirm quantities with the manufacturer or paint professional. Metric mode reports liters using m² per liter.