Paint Calculator
Estimate wall area, subtract doors and windows, and calculate paint volume from coverage efficiency — like Omni Calculator.
Room dimensions
Doors
Windows
Amount of paint needed
0.88 gal
Formula
How it works
Examples
About this calculator
The Paint Calculator estimates how much interior wall paint you need based on room size, doors, windows, coats, and coverage efficiency. It follows the same wall-area approach used by popular construction estimators.
Room dimensions or wall area
Calculate from length, width, and height—or enter total wall area directly if your room is not a simple rectangle.
Door & window deductions
Subtract opening area automatically so you do not over-order paint for surfaces you are not coating.
Imperial or metric units
Switch between feet/gallons and meters/liters, and optionally estimate total paint cost from price per unit.
- Bedroom repainting
- Whole-home projects
- Contractor material lists
- DIY budget planning
Frequently asked questions
Quick answers about this calculator—how it works, accuracy, and everyday use.
Enter the room length, width, and height to estimate total wall area, then subtract doors and windows. Multiply the net wall area by the number of coats and divide by the paint coverage rate on the can (typically sq ft/gal or m²/L).
No. This tool estimates wall area only. If you plan to paint the ceiling, add extra paint based on the ceiling square footage and your product's coverage rate.
Yes. Porous, textured, or unpainted drywall can require 10–30% more paint. Complicated trim and touch-ups also use extra product, so buying slightly more than the estimate is usually smart.
Use the coverage figure printed on your paint can. Interior latex often covers about 350–400 sq ft per gallon on smooth drywall, but always follow the manufacturer's label for the most accurate estimate.