A ruler on your phone, at real size
Open this page on your phone, put the object against the top edge of the screen and drag on the scale until the line meets its end. The reading is in centimetres or inches, to the nearest millimetre or sixteenth.
- Check the status line. On most iPhones it's already set. Everywhere else, set it once with a bank card.
- Line the object up with 0 at the top edge of the screen.
- Drag on the scale. You'll feel a tick at every whole centimetre or inch.
Questions
Is an online ruler accurate?
Only if it knows your screen. Browsers draw 96 pixels to an inch on every device, so a plain ruler image is often 10 to 40 percent off. True Size sets the scale from your iPhone model or from a bank card you hold to the screen.
How do I check it?
Hold a bank card against the screen. Its long side is 85.6 mm. If the scale reads 8.6 cm at the card's edge, you're set.
What can I measure?
Anything shorter than your screen: screws, bolts, beads, coins, cable ends, buttons, small parts. For longer things, measure in two passes or use a tape.
Does it work on Android and computers?
Yes. Set it once with a card. The setting stays in this browser on this device.
Why is it off on my iPhone?
Display Zoom (Settings, Display and Brightness) changes the screen scale. Turn it to Default or set the ruler with a card.
Ruler for your iPhone
Each page is set for that model's screen, so it is the right size the moment it opens.
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