Yes, completely free with no signup required.

Does my data leave my device?

No. Everything runs in your browser — nothing is sent to a server.

Does it work on mobile?

Yes, but physical accuracy depends on your device's reported DPI. Use the calibration slider for best results.

A calibrated on-screen ruler for measuring objects placed against your display.

100% client-side · no upload

Unit: cm inches

Screen DPI: (adjust to calibrate)

Tip: place a credit card (85.6 mm / 3.37 in wide) against the ruler and adjust DPI until they match.

Select cm or inches and place an object against the ruler on your screen.
For accurate measurements, calibrate using a known-size object (e.g. a credit card) by adjusting the DPI value.
Read off the measurement where your object ends.

Is this tool free?: Yes, completely free with no signup required.
Does my data leave my device?: No. Everything runs in your browser — nothing is sent to a server.
Does it work on mobile?: Yes, but physical accuracy depends on your device's reported DPI. Use the calibration slider for best results.