How to see a phone's true size on your screen
A website cannot measure your screen, so a phone drawn in "millimetres" on a web page is usually the wrong size. A quick calibration with a bank card fixes that.
Why web pages get the size wrong
Web pages are drawn in CSS pixels, which are not a fixed physical size. How many pixels fit in a real millimetre depends on your screen, its resolution and your display scaling. Without that number, a site can only guess.
The bank card trick
Every standard bank card (ISO/IEC 7810 ID-1) is 85.60 mm wide and 53.98 mm tall. If you match an on-screen card to a real one, the page knows exactly how many pixels equal a millimetre on your screen.
Steps
- Open the size tool and choose Life size.
- Tap Calibrate.
- Hold a real bank card flat against your screen.
- Drag the slider until the outline on screen is exactly the size of your card.
- Tap Save size. Your choice is remembered on that device.
On a narrow phone screen the card outline turns sideways so it fits. Match the edge you can see.
Tips for accuracy
- Do not zoom the page. Browser zoom changes the scale, so calibrate again if you change it.
- Different screens need their own calibration, including an external monitor.
- For a quick estimate, pick your device in the calibration window instead of using a card.
Compare with your real phone
On a computer or tablet, place your actual phone against the screen next to the on-screen outline of the one you are thinking of buying. It is the closest you can get to holding the phone in a shop.