Why can't my browser tell me my screen size?
Browsers report pixels, not inches (or centimeters). A 24 inch and a 27 inch screen at the same resolution look the same to a website. Matching a card of known size tells us how many pixels fit in one inch on your screen.
How accurate is the card method?
Very accurate when the outline matches the card edge closely. One pixel of slider error changes the result by about 0.3%. On a 27 inch (69 cm) screen that is under 0.1 in (0.25 cm).
Hold the card flat and look straight at it, because viewing at an angle makes the card look smaller.
Which edge of the card should I match?
On a computer, match the long edge, 85.60 mm (3.37 in). On a phone held upright, match the short edge, 53.98 mm (2.13 in), so the card fits across the screen.
How do I check my laptop screen size?
There are three quick ways, and they should agree within a tenth of an inch.
- Use the card tool above. It works on any laptop with a browser and gives the size in inches and centimeters.
- Look up the model. On a Mac, open the Apple menu and choose About This Mac, which names the size, such as 13 inch. On Windows, the model number is on the sticker under the laptop, and its spec sheet lists the screen.
- Measure it. Run a tape from one corner of the lit screen to the opposite corner, leaving out the frame.
Our laptop dimensions pages list common sizes and what they measure across and up.
How do I find my monitor size in Windows?
Windows does not show the size in inches, but it does show the monitor’s name. Open Settings, then System, Display and Advanced display. The model under Display information often includes the size, as in many Dell, LG and Samsung model numbers that start with 24, 27 or 32.
The same model number is on the label on the back of the monitor. Search for it to find the screen size, or look it up in our monitor dimensions pages for the width and height of common sizes.
Is screen size measured with the frame?
No. The size is the diagonal of the picture area only, from corner to corner. The frame around it adds to the width and height of the monitor, but not to the screen size.
Questions
Does any card work?
Any card in the ID-1 size works, which covers bank, debit and credit cards. Store cards and some ID cards use it too, so check that yours is 85.60 x 53.98 mm before you rely on it.
Why is my result a little different from the size on the box?
Product names often round the screen size, and an outline that is a pixel or two off shifts the result slightly. Nudge the outline with the minus and plus buttons until it matches the card exactly.
Is my result saved?
Only for this visit, in your browser. Close the tab and it is gone, and nothing is sent to us.
How we measure
Pixels per inch = outline width in pixels ÷ card edge in inches. Diagonal = the screen's diagonal in pixels ÷ pixels per inch, and physical pixel density multiplies that by your pixel ratio.