Hinge Caliper

Hinge Caliper turns the hinge of iPhone Duo into a measuring tool.

IMPORTANT: The caliper and protractor use the iPhone Duo hinge and only work on iPhone Duo. On other iPhone models, only the bubble levels and on-screen rulers are available.

CALIPER (iPhone Duo only)
Close your iPhone Duo on an object so it touches the outer edges of both halves. Hinge Caliper works out the object's thickness from the hinge angle. Hold still for a moment and the reading locks: your iPhone vibrates and speaks the measurement and hinge angle, so you don't need to see the screen. For best accuracy, calibrate once with an object of known size.

PROTRACTOR (iPhone Duo only)
See the exact opening angle of your iPhone Duo, from 0° to 180°, on a clear protractor dial.

OUTER DISPLAY (iPhone Duo only)
Optionally show the angle and caliper reading on the outer display while you work. iOS only allows this while the camera is running. Nothing is recorded or saved, and it's off until you turn it on.

RULERS (all iPhone models)
Centimetre and inch rulers run along the screen edges. On iPhone Duo they're true scale on both displays. Double-tap a ruler to swap which unit sits against the edge. Fine-tune the scale with any bank card. On other iPhone models, calibrate with a bank card first.

LEVELS (all iPhone models)
Horizontal and vertical bubble levels, with a plumb mode when your iPhone stands upright.

Measurements are approximate and depend on your device's sensors. Don't use Hinge Caliper where precise measurements are critical.

No data collection. No ads. Works offline.

Requires iOS 17 or later. The caliper, protractor and outer display require iPhone Duo.