Paint Calculator

Use this free paint calculator to estimate wall paint gallons from room dimensions, doors, windows, coats, coverage, and extra percent.

All tools

Research-backed assumptions Formula steps Examples included Private in-browser use

Room length feetRoom width feetWall height feetDoorsWindowsCoatsCoverage ft2 per gallonExtra percent

Paint to buy2 gallons

12 ft x 10 ft room, 2 coats

Paintable wall area: 302 ft2
Gallons before rounding: 1.8982857143
Coverage used: 350 ft2/gal

Actual paint use changes with product, surface texture, primer, color change, and application method.

Formula steps

Find wall area from room perimeter times wall height.
Subtract estimated openings using 20 square feet per door and 15 square feet per window.
Multiply by coats, add extra percent, divide by coverage, then round up gallons.

How to use the paint calculator

Enter room length, width, wall height, doors, windows, coats, paint coverage, and extra percent.
Press Estimate paint to see paintable wall area, calculated gallons, and whole gallons to buy.
Use the coverage number from your paint can or product page when possible.
Surface texture, primer, color change, and application method can change actual paint use.

Common uses

Estimate gallons for a bedroom, office, or living room.

Adjust for one or two coats before buying paint.

Subtract common doors and windows from wall area.

Compare coverage values from different paint labels.

Examples

Bedroom 12 x 10 x 8 ft, 1 door, 2 windows, 2 coats

Gallons to buy

Living room 18 x 14 x 9 ft, 2 doors, 3 windows, 2 coats

Paintable area and gallons

Accent wall planning 10 x 8 ft wall, 1 coat, 350 ft2/gal

Low paint estimate

Frequently asked questions

Plain-language answers about when to use the tool, what it does with your inputs, what to double-check, and how privacy works.

When should I use the Paint Calculator?

Use it when your task matches one of these common needs: Estimate gallons for a bedroom, office, or living room. Adjust for one or two coats before buying paint. It works best when you already know the values, dates, units, or settings the page asks for.

What is the Paint Calculator doing with my inputs?

In plain language: The calculator finds wall area from room perimeter and height, subtracts estimated doors and windows, multiplies by coats and extra percent, then divides by square-foot coverage per gallon. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.

What should I double-check before trusting the answer?

Paint coverage depends on product, primer, surface texture, color change, application method, and how much paint remains in the can or tray. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.

Does the site save what I enter?

No. The calculator runs in your browser tab. Your recent answers stay only on the page while you use it, and they are not sent to a server.