Online Ruler
A free online ruler in centimeters and inches. Calibrate it to your screen with a bank card for real-world accurate measurements.
This tool is being rebuilt natively. You can use the current version now:
How to use Online Ruler
- Choose cm, inch, or both.
- Calibrate: hold a bank/ID card to the box and drag the slider until it matches.
- Measure anything against the on-screen ruler.
About Online Ruler
Online Ruler is a free Becoderr tool. It needs no sign-up, runs fast and privately, and works right in your browser for most tasks. For the few server-based tools, your files are processed in memory and discarded immediately after the operation.
Frequently asked questions
How accurate is the online ruler?
After you calibrate it with a standard bank card (85.6 mm wide), the ruler matches real-world size on your screen. Without calibration it uses a 96 PPI default.
Does it save my calibration?
Yes. Your PPI calibration is stored in your browser, so the ruler stays accurate on your next visit on this device.
Is this tool free to use?
Yes. Every tool on Becoderr is completely free with no sign-up required. Signed-in users get higher file-size limits.
Are my files safe?
Yes. Browser-based tools process files entirely on your device; nothing is uploaded. Server-based tools process files in memory and discard them immediately after the operation.
Is there a file size limit?
Server-based tools accept up to 5 MB for anonymous users and 50 MB when signed in. Browser-based tools are limited only by your device.