Find wall area
Room wall area is the perimeter multiplied by wall height. Known-area mode starts from the area you enter.
Tool Switcher: Paint
Project toolsTools
Measure twice. Buy once.
Paint Project Calculator
Estimate wall area, coats, openings, containers, and optional cost—with every assumption visible.
- US and metric units
- Editable coverage
- Exact and purchase quantities
Project calculator
Paint Calculator
Estimate wall area, paint volume, containers, and optional material cost.
Methodology
How this paint estimate works
Subtract openings
The combined area of doors and windows is removed before coats and coverage are applied.
Apply coats and coverage
Net wall area × coats ÷ product coverage gives the exact paint volume.
Round for purchase
The planning allowance is applied before the result rounds up to whole containers.
Worked example
A 12 × 10 ft room with 8 ft walls
352 ft²gross wall area
−42 ft²doors & windows
=310 ft²paintable area
With two coats, 375 ft²/gal coverage, and a 10% planning allowance, the estimate is 1.82 gallons. Buy two one-gallon cans.
Frequently asked questions
A second look at the estimate.
Should doors and windows be subtracted?
Subtract openings you will not paint. Leave trim and doors in the estimate when they receive the same product.
Why can coverage vary?
Texture, porosity, color change, application method, and product type can all change practical coverage.
What should I round up to?
The calculator rounds to the container size you select. Confirm the sizes stocked for your product.
Sources and limitations
This tool provides a planning estimate, not a product guarantee. Product instructions take priority.
Last reviewed: July 17, 2026