About Paint Calculator

Enter your room's length, width, and wall height — plus doors, windows, coats, and coverage — and the calculator estimates the paint you need. Results are shown in both gallons and liters. Everything runs in your browser: nothing is uploaded, and no account is required.

The tool supports three kinds of estimate:

• Quick room estimates — wall area from a rectangular room, with standard door and window sizes.
• Detailed interior estimates — individual walls, custom-sized doors and windows, optional ceiling and trim paint.
• Exterior estimates — one elevation per side of the house, with its own doors, windows, and optional trim.

Doors and windows are deducted from the wall area automatically. The coverage rate (square feet per gallon) is editable to match the paint you plan to buy, and an optional price per gallon produces a cost estimate. A purchase recommendation rounds the result up to whole 1-gallon cans. Estimates can be shared via a link that carries the calculator settings, and a 3D preview of the room renders entirely in your browser.

Estimating paint is simple arithmetic, but most people don't want to do it by hand in the paint aisle. Paint-brand calculators are often slow, buried inside store sites, or unavailable. This site was built as a fast, focused, neutral alternative: one page, the math, and results in seconds — with no brand upsell and no account wall.

It is a single-purpose tool, deliberately. No bloated feature set, no signup, no cost.

The calculation follows the standard formula: (wall area − openings) × coats ÷ coverage. Wall area comes from your dimensions; openings (doors and windows) are subtracted; the coat count multiplies the paintable surface; and the result is divided by the coverage rate you enter — 350 sq ft/gal by default for interior paint and 300 sq ft/gal for exterior, both editable.

The result is an estimate, not a promise. It reflects the dimensions and settings you enter, nothing more.

Paint Calculator provides estimates based on the measurements and settings entered by the user. Actual paint usage varies by product, surface, application, and conditions.

Check the manufacturer's product data for the specific paint you're using, and see your terms for full details on how estimates should be used.