Calibrated Phone Screen Ruler
Choose your exact iPhone or Samsung model, then enter full screen to build a ruler from the known physical display—not the phone body. A bank-card check remains available for maximum precision.
Three steps from phone to mouse test
- 01
Identify the screenSelect your exact model, or enter its advertised diagonal size.
- 02
Build the rulerTap the full-screen button and keep the phone out of split-screen mode.
- 03
Transfer 50 mmMark the displayed 0–50 mm span beside the mouse, then choose “Phone ruler · 50 mm” on the computer.
Choose your exact phone model
We use the manufacturer's display resolution and pixel density or full-rectangle diagonal to calculate the active screen rectangle. We never use the phone's body length or width.
Enter the advertised screen size, not the phone body. Full screen supplies the width-to-height ratio automatically.
The button first enters full screen, then reads the full-screen viewport. A selected model supplies official display data; a manual diagonal uses the measured full-screen aspect ratio. On iPhone browsers that cannot enter true full screen, a non-split, full-width viewport is used as the safe fallback.
Match a bank card's short edge
Hold the short edge of a standard bank card against the box below. Move the slider until both widths match exactly. No card details are read or entered.
Know the exact active screen width instead?
Enter the physical width of the illuminated screen—not the phone body. Resolution, pixel ratio, and refresh rate alone are not enough.