PROTRACTOR DUOA new use for your fold.

Find your
angle.

Your iPhone is the angle finder.
Open it, line it up, and let the fold
do the measuring.

Coming soon

Exclusively for iPhone Duo · iOS 27.1

A little tool. A closer look.
A folding phone as an angle finderAn interactive illustration of a phone opened to 87 degrees. Move the slider below to change its fold.87°OPPOSITE 93°Record◷ History018087°

Interactive illustration. Try the slider, not a live measurement.

  1. 01

    Open.

    Unfold your iPhone Duo.

  2. 02

    Line up.

    Match each half to your angle.

  3. 03

    Read.

    See the hinge angle as it changes.

  4. 04

    Save.

    Tap Record to keep the reading.

A FOLD. A READING. THAT’S IT.

A little more useful.
In the real world.

A line you’ve drawn. A corner you’re curious about.
Two simple ways to put your phone to work.

01 On paper

87°
Painted illustration of a folding phone standing on paper, with its lower edges aligned to two lines and an example angle of 87 degrees.

From pencil lines to degrees.

Stand the phone on its bottom edges. Align each edge with a line on the paper, then read the angle.

02 On surfaces

135°
Painted illustration of a folding phone with each half resting against a different surface, showing an example opening of 135 degrees.

Let the fold follow the corner.

Rest each half against a surface. Fold to fit the angle where they meet, with controls on the flatter half.

Protractor reads the phone’s hinge angle. How you line up the phone, including its edges and case, affects the angle you’re measuring.

FOR THE ANGLES WORTH KEEPING

Measure now.
Remember later.

Tap Record when you’ve got your reading. Find it again in History, grouped by day with the time it was saved.

Your readings stay with you.Saved on your device. No account needed.

Illustrative readings, not an app screenshot.

BEFORE YOU OPEN UP

Good to know.

Which iPhone do I need?

Protractor Duo is built exclusively for iPhone Duo running iOS 27.1. It uses the phone’s folding hinge to measure the opening angle.

What does it measure?

The live hinge angle as you fold the phone. An opposite-angle reading shows 180° minus that angle. The guides help you line it up with paper or surfaces; it doesn’t measure a surface’s slope.

How accurate is it?

Use the reading as an estimate. As a rule of thumb, allow around ±5° in the hinge reading; that’s an approximate allowance, not a guaranteed tolerance. Alignment, rounded phone edges, and a case can add more error when measuring lines or surfaces.

Line up both halves carefully and hold the phone still before recording. For work that needs a precise angle, check with a dedicated measuring tool. Apple’s documentation explains that hinge updates can vary in granularity and shouldn’t be relied on for a fixed precision.

Where are my readings saved?

Your readings and preferences stay on your device. History groups your saved readings by day, and you can delete individual readings or clear them all.

Can I download it yet?

Not just yet. Protractor Duo is coming soon. Have a question? Write to [email protected].

Protractor Duo app icon

PROTRACTOR DUO

Open up.
Find your angle.

Coming soon for iPhone Duo

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