kakdo° is a $1 protractor app that reads the iPhone Duo hinge angle live and measures angles in photos. The live readings work with an iPhone Duo, while the photo tools run on any iPhone or iPad with iOS or iPadOS 26.5 or later.
Developer Hiroto Mugikura released the app on the App Store on October 15, and version 1.3 on October 27 added a dual-display mode with a live camera alignment preview. It sits alongside Hinge Angle Meter, adding a photo protractor and calibration.
kakdo° shows the hinge angle live and can be calibrated
On an iPhone Duo, the number follows the hinge as it opens and closes, and the app shows the opening angle together with its supplementary angle. Version 1.3 lets you double-tap the angle readout to switch between the two.
The same update added an optional dual-display mode. It adds a live rear-camera alignment preview and, when available, shows the same angle on the outer display. The app asks for camera permission only when you turn the mode on, and the preview is not recorded or saved.
Version 1.2 added on-device calibration, which compares the hinge readings with a reference angle you enter from a physical instrument and uses static measurements. Corrections can be switched on only after separate validation measurements pass. The calibration profile is tied to that installation, hardware model and iOS version, stays out of backups, and can be disabled or reset.
Photo angles work on any iPhone or iPad with iOS 26.5 or later
In a photo, you place points on an angle that catches your eye and kakdo° measures it, and one image can hold several angles. The editor gives the photo more room, shows a short cue for each point and lets you fine-tune point positions with continuous control.
You can add notes, save the measurements on the device, reopen and edit them later, or share a PNG image or a CSV file. The app imports only the photos you choose or take and does not ask for access to your whole photo library.
Photo measurements are 2D angles in the image plane, so the viewing direction and where you place the points can make them differ from the real object’s angles. Version 1.1 added a four-page guide.
The app is a one-time $1.00 purchase with no ads or subscriptions. It is a 5.5 MB Utilities app rated 4+ that comes in English and 15 other languages, and up to six family members can use it through Family Sharing.
