What Is My Screen Size

How to measure your screen size

1. Set the browser zoom to 100% (Ctrl+0, or Cmd+0 on a Mac).
2. In Calibrate to your screen, hold a bank, ID or loyalty card flat against the screen. Drag the slider until the dashed box is exactly as wide as the card, then press Use this size. On a phone in portrait, match the card's short side.
3. Read the diagonal at the top, with the width and height in inches and centimetres.
4. To find the size of a screen you are not using, enter its diagonal and ratio in the Screen size calculator.

What the results mean

Screen sizes are always the diagonal of the visible picture, from one corner to the opposite corner, without the bezel. Monitors and TVs are sold as 24", 27", 55" and so on; laptops as 13.3", 14", 15.6" or 16"; phones as about 6.1" to 6.9".

With a good card match the measurement is usually within 2-3% of the real size, enough to tell a 15.6 inch laptop from a 14 inch one. If the page says the screen is not calibrated, it is guessing from the web standard of 96 pixels per inch, which can be far off on laptops and phones.

Two other things to know: the browser measures the whole screen, so a notch or rounded corners on a phone are counted; and a few screens report a scaled size that is not quite exact, so if the result is a little off a common size (14.1" for a 14" laptop), it is that size.

Other ways to find your screen size

Measure with a tape: from the bottom left corner of the picture to the top right, not including the frame, and divide centimetres by 2.54 for inches. Check the model: on Windows, Settings > System > About shows the model name, and a search for it gives the size; on a Mac, Apple menu > About This Mac shows the size in the model name (for example "MacBook Pro 14-inch"); on a monitor or TV, the model number usually contains the size, such as 27 in "S27..." or 55 in "...55...". Phones: the what phone do I have page names your model.

Diagonal, width and height

For the same diagonal, a wider ratio gives a wider but shorter screen. A 27 inch 16:9 monitor is 59.8 x 33.6 cm; a 27 inch 16:10 one is 58.2 x 36.4 cm. That matters when comparing a 34 inch ultrawide (21:9, about 80 x 33 cm) with a 27 inch 16:9: the ultrawide is much wider but about the same height. The calculator above works out width, height and area for any diagonal and ratio, and the aspect ratio calculator does the same for pixel sizes.

Common problems and fixes

The size is clearly wrong

Reset the browser zoom to 100% and calibrate again, pressing the card flat against the glass. Make sure you used "Use this size" after moving the slider.

I have no card

Any card of standard size works: bank, ID, driving licence, library or loyalty card (85.60 x 53.98 mm). Or use a ruler and the fine tune buttons in the online ruler, which shares the same calibration.

I have two monitors

The page measures the screen its window is on. Drag the window to the other monitor, then calibrate on that screen.