Paint Calculator

How to use this calculator

Enter Length (ft), Width (ft), Wall height (ft), Coats, Coverage per gallon (sq ft). The result updates in your browser as you edit an input. The prefilled values are examples only.

How the estimate works

Calculate wall area as 2 × (length + width) × wall height, multiply by coats, then divide by coverage per gallon. The result includes all four walls before openings. To deduct doors or windows, calculate net wall area in a separate worksheet, multiply by coats and divide by the selected coverage; this interface has no opening-area input.

What can change the answer?

Doors, windows, textured walls, primer, and how heavily you apply paint all affect actual coverage. Check the can label and allow for touch-ups if a matching color will be hard to find later.

Before relying on the result

Check room dimensions in feet, coat count and the selected paint’s coverage per gallon. The result covers rectangular-room walls before openings; it does not include ceiling or trim. This interface has no door or window deduction field. Use a separate wall-area worksheet for a net-area estimate, and round the purchase to the available container sizes.

Worked example with the default inputs

A 12-by-10-foot room with 8-foot walls has 352 square feet of wall area before openings. Two coats require 704 square feet of coverage; at 350 square feet per gallon the estimate is 2.01 gallons. Buying whole containers requires a separate rounding decision.

Interpret the result in a planning record

Measure the room perimeter and wall height, choose the number of coats, and enter the coverage per gallon from your paint label. The paint calculator estimates wall coverage before large openings are subtracted. A textured wall or a strong color change may need a different plan from a smooth wall with a similar existing color. Ceiling paint should be estimated separately.

Save the input values, units and result together. Change one uncertain input at a time so you can see which assumption moves the answer. A displayed decimal is arithmetic precision, rather than evidence that the measurements or rates are equally precise.

More tools

Read the How to Measure a Project Before Buying Materials guide →