PROJECT GUIDE
Paint Calculator for a Room
A room paint estimate starts with wall area, then subtracts major openings and accounts for the number of coats and the paint’s stated coverage. Use the calculator as a planning estimate, not a guarantee of actual coverage.
Calculate wall area
For a rectangular room, wall area is approximately 2 × (length + width) × wall height. This estimates the four walls before subtracting doors and windows.
Subtract openings
Measure the approximate area of doors, large windows and other openings that will not be painted. For detailed projects, calculate each opening separately and add them together.
Account for coats
Multiply the paintable wall area by the number of coats. Coverage per gallon is then used to estimate gallons. The product label is more useful than a generic coverage number because paint type and surface conditions vary.
Why real coverage varies
Porous surfaces, texture, color changes, application method and the condition of the wall can all change coverage. Dark-to-light color changes may require different preparation or coats than a simple repaint.
Before buying
Check the exact product’s stated coverage and recommended number of coats. Round up to the package size you can actually buy, and keep a record of the product name and color for future touch-ups.
Use the calculator
Ready to run the numbers? Use the BuildPlanTools calculator, then compare the estimate with the product label, supplier information and project requirements.
These estimates are for general planning. Product specifications, site conditions, local requirements and professional recommendations should take priority where applicable.