Apple lists the iPhone Duo at 5.2 mm thick open and 11.3 mm thick closed, with a weight of 254 grams. Double the open figure and you get 10.4 mm, which leaves 0.9 mm of the closed measurement that Apple never breaks down.
Those two numbers are the whole proposition of a folding phone in one line: open, the iPhone Duo is thinner than any iPhone Apple sells, and closed it is thicker than all of them. Everything Apple has published about the hinge and the enclosure sits between the two figures.
Key facts: every dimension Apple publishes for iPhone Duo
| Measurement | Apple’s figure |
|---|---|
| Width, open | 164.6 mm (6.48 inches) |
| Height, open | 117.8 mm (4.64 inches) |
| Thickness, open | 5.2 mm (0.21 inches) |
| Width, closed | 84.1 mm (3.31 inches) |
| Height, closed | 117.8 mm (4.64 inches) |
| Thickness, closed | 11.3 mm (0.44 inches) |
| Weight | 254 g (8.96 oz) |
| Frame and hinge cover | Grade 5 titanium with a mirror-polished finish; hinge cover 3D printed from 100 percent recycled titanium |
| Hinge | More than 100 components, with custom adhesives for flex relief |
| Water and dust | IP68, to a maximum depth of 6 meters for up to 30 minutes |
Why 11.3 mm is not simply twice 5.2 mm
A folded phone is two halves of itself plus whatever holds them together. Two 5.2 mm halves come to 10.4 mm, and Apple publishes 11.3 mm, so 0.9 mm belongs to something else.
Don’t miss the best of The Mac Observer
Set us as a preferred source and our Apple reporting ranks higher in your Google Search results and Discover feed — one tap, no account changes.
Apple does not say what. What it does describe about that region is a hinge of more than 100 components, custom adhesives that relieve bend stress, and a hinge cover 3D printed from 100 percent recycled titanium.
Part of the difference may be rounding. Apple’s tech specs give the same dimensions in inches, at 0.21 inches open and 0.44 inches closed, and 0.21 doubled is 0.42 rather than 0.44, so the published pair does not reconcile exactly in either unit.
Apple also never states where on the body either thickness is measured, which matters on a phone with a raised camera housing. The figures are Apple’s, the arithmetic is ours, and the gap is real in both sets of units.
Open, it is thinner than the thinnest iPhone in the lineup
Apple’s product page calls the iPhone Duo the thinnest iPhone, and the arithmetic supports it in the open state: 5.2 mm against the 5.64 mm iPhone Air, a difference of 0.44 mm.
Against the phones announced alongside it the gap is much wider. The iPhone 18 Pro and iPhone 18 Pro Max are both 8.75 mm thick, which makes the open Duo 3.55 mm thinner than either.
| Device | Thickness | Weight |
|---|---|---|
| iPhone Duo, open | 5.2 mm | 254 g |
| iPhone Air | 5.64 mm | 165 g |
| iPhone 17 | 7.95 mm | 177 g |
| iPhone 18 Pro | 8.75 mm | 211 g |
| iPhone 18 Pro Max | 8.75 mm | 249 g |
| iPhone Duo, closed | 11.3 mm | 254 g |
| Apple Watch Ultra 4 case | 12 mm deep | 63.0 g |
Closed, it is 2.55 mm thicker than an iPhone 18 Pro
The closed figure is the one that decides how the phone lives in a pocket, and it is 11.3 mm against 8.75 mm for both iPhone 18 Pro sizes. That is 2.55 mm more, or a little under a third again.
Weight moves far less. At 254 grams the Duo is 5 grams heavier than the 249-gram iPhone 18 Pro Max and 43 grams heavier than the 211-gram iPhone 18 Pro, which is a smaller spread than the thickness suggests, as the Duo against the Pro Max comparison shows.
For a sense of scale outside the iPhone line, the 49 mm Apple Watch Ultra 4 case is 12 mm deep. The closed Duo is 0.7 mm thinner than that case.
The width behaves the same way as the thickness
Apple lists the same height, 117.8 mm, open and closed, so the fold runs along the short axis and the width is what halves. Open it is 164.6 mm wide, closed 84.1 mm.
Half of 164.6 mm is 82.3 mm, so the closed width is 1.8 mm more than half the open width, the same kind of remainder as the 0.9 mm on thickness. Apple describes the open shape as a wide, passport-like format and leaves the spine unmeasured.
What Apple has not said
Apple has published no fold-cycle rating, no thickness for the hinge assembly, no closed-gap figure, and no note on where either thickness is measured. It has also published no repair pricing for any product announced on September 9, which was covered across our event recap.
Nobody outside Apple has handled an iPhone Duo, so none of those blanks can be filled in by measurement yet. Pre-orders open Friday, October 16 at 5 a.m. PT, with availability from Friday, October 23 in more than 70 countries and regions and 28 more on Friday, October 30.
