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Free Paint Calculator

Estimate gallons or litres of paint for a room's walls, ceiling and number of coats.

Wall area is the room's perimeter times wall height, minus 20 sq ft per door and 15 sq ft per window, with the ceiling optionally added. That area times the coats, divided by coverage per gallon and increased by waste, gives the paint needed.

How to use the Paint Calculator

  1. Enter the measurements of the area you are working on.
  2. Read the amount of material needed, including a waste allowance where relevant.
  3. Round up when you buy, and check the figures with your supplier.

About the Paint Calculator

Estimate gallons or litres of paint for a room's walls, ceiling and number of coats.

Home and building jobs are easier to price when you know how much material you really need. A quick estimate also helps you avoid buying too little or too much.

Getting started with the Paint Calculator

Using the paint calculator takes a minute or two. Your entries are saved in this browser, so you can come back later and carry on.

Tips for better results

Rough or porous walls absorb more paint, so pick the lower coverage setting. Buy paint for all rooms from the same batch, and add a little for touch-ups.

Add 5 to 10 percent for waste, cuts and mistakes.

Measure twice, order once, and check quantities with your supplier.

Privacy and where your data goes

Everything you type into the paint calculator stays on your own device. Zapxa does not receive your numbers or documents. If you clear your browser data, your saved entries will be removed, so download a PDF of anything you want to keep.

Frequently asked questions

How much area does a gallon of paint cover?

The calculator defaults to 350 sq ft per US gallon, with 250 for rough walls and 400 for smooth ones. Your paint's label gives the manufacturer's figure.

Does it subtract windows and doors?

Yes, it deducts an assumed 20 sq ft per door and 15 sq ft per window. Large or unusual openings may need a manual adjustment.

Is the paint calculator free?

Yes. It is free to use with no signup, no watermark and no usage limits.

Is my data private?

Yes. Your inputs are processed in your browser and saved only in its local storage. They are not uploaded to our servers.

Does it work on mobile?

Yes. Zapxa works on phones, tablets and desktops. Use the print button or download a PDF to keep a copy.

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