The iPhone Duo is the first iPhone that is two different sizes. Folded, it is a short, thick slab smaller than a passport. Open, it is a thin, wide tablet in landscape. A case has to work in both states, across a hinge, on a device whose two halves are each just 5.2 mm thick.
This page collects every published dimension in one place, puts them into terms you can picture, works out what a case does to them, and explains why a fraction of a millimetre decides whether a case fits. It is the reference the rest of our guides point to.
Folded: 84.1 × 117.8 × 11.3 mm. Open: 164.6 × 117.8 × 5.2 mm. Weight: 254 g.
With a typical case: roughly 13–15 mm folded and 285–315 g, depending on construction.
Compatibility: only cases made specifically for the iPhone Duo fit. Galaxy Z Fold 8 cases do not.
Full dimensions
| Measurement | Folded | Open |
|---|---|---|
| Width | 84.1 mm ✅ | 164.6 mm ✅ |
| Height | 117.8 mm ✅ | 117.8 mm ✅ |
| Thickness | 11.3 mm ✅ | 5.2 mm ✅ |
| Weight | 254 g ✅ | |
| Display in use | 5.4″ outer | 7.6″ folding inner |
| Orientation | Portrait | Landscape |
| Frame | Grade 5 titanium ✅ | |
✅ Confirmed from Apple's published specifications. In inches: 3.31 × 4.64 × 0.44 in folded, 6.48 × 4.64 × 0.20 in open, 8.96 oz.
What those numbers look like
Millimetres are hard to picture. These comparisons use objects with fixed international sizes, so they hold anywhere in the world.
| Compared with | Its size | The iPhone Duo |
|---|---|---|
| A bank card (ID-1) | 85.6 × 54.0 mm, 0.76 mm thick | Folded, the Duo is 1.5 mm narrower than a bank card is long. Open, each half is 5.2 mm — about seven stacked bank cards |
| A passport (ID-3) | 88 × 125 mm | Folded, the Duo is smaller than a closed passport on both sides — 3.9 mm narrower, 7.2 mm shorter |
| Galaxy Z Fold 8 | 81.9 × 123.9 × 9.7 mm folded, 201 g | The Duo is 2.2 mm wider, 6.1 mm shorter, 1.6 mm thicker and 53 g heavier |
The passport comparison is the useful one. It explains why the wide foldable format is sometimes called "passport-style": folded, the iPhone Duo genuinely fits within a passport's outline. If a passport fits your jacket pocket, a folded Duo will too — though at 11.3 mm it is noticeably thicker than one.
Three things the numbers reveal
Apple publishes the dimensions without explaining them. Working through them shows three things about how the device is built, each of which matters for a case.
1. It closes almost flat
Folded thickness = 11.3 mm
Difference = 0.9 mm
Folding two 5.2 mm halves together would give 10.4 mm if they met perfectly. The real figure is 11.3 mm, so just 0.9 mm accounts for the hinge mechanism and the bend of the display. The device closes essentially gapless. For a case, that is a strict constraint: anything placed between or on the inner faces will stop it closing flat — which is why a card sleeve inside a folio is a fault on this device, not a feature.
2. The halves overlap at the hinge
Open width = 164.6 mm
Difference = 3.6 mm
Doubling the folded width overstates the open width by 3.6 mm, because the hinge and frame are shared between the two halves rather than duplicated. This is why case makers cannot simply design two independent slab shells: the spine is a shared region, and how a case handles it is the main thing that separates a good Duo case from a poor one.
3. Both screens have the same shape
Open: 164.6 ÷ 117.8 = 1.40 (landscape)
The folded device and the open device have the same proportions, turned through 90 degrees. Apple describes the two displays as sharing the same aspect ratio, and the outer dimensions confirm it. For cases, it means the open device sits in landscape — so a stand needs to prop it that way, which is why we recommend rotating ring stands or landscape-oriented kickstands. Our stand case guide covers this in detail.
What a case does to the size
A folded iPhone Duo in a case is covered on both outside faces — the back panel and the frame around the outer display. Add those two wall thicknesses to 11.3 mm and you have the folded size. Set the values below, or pick a preset.
Case size calculator
Presets are illustrative ranges for each construction type, not measurements of specific products. Raised lips, rings, card pockets and kickstands add height on top of the wall thickness, so cases with those features can be thicker than the calculator shows.
Why thickness matters more on a folded phone
Folded, the iPhone Duo already starts at 11.3 mm — thicker than a typical conventional phone before any case goes on. A case therefore pushes it from "thick phone" towards "small book" territory: a slim case takes it to around 13.5 mm, a wallet or kickstand case to 15 mm or more. Open, the extra matters less, because the case wall sits on two 5.2 mm halves you hold flat. The practical rule: the more you carry the Duo folded in a pocket, the more a slim case is worth — so choose the protection level deliberately. Our hinge protection guide sets out the four coverage levels and what each costs in thickness.
Published case thicknesses
Few makers have published iPhone Duo case dimensions. These are the figures available, from each brand's own listing.
| Case | Published thickness | Published weight | Source |
|---|---|---|---|
| Thinborne aramid case | 0.90 mm | Not published | Brand listing |
| Latercase MagLock case | 1 mm | Not published | Brand listing |
| PITAKA Edge Case | ~1.2 mm (some variants ~1.3 mm) | ~22 g (some variants ~19 g) | Brand listing |
| Apple iPhone Duo Case | Not published | Not published | Apple |
| Apple Folio with Kickstand | Not published | Not published | Apple |
| Duo Case Co range | Measuring after launch | Measuring after launch | Published here after 23 October |
Why other foldable cases don't fit
The iPhone Duo and Samsung's Galaxy Z Fold 8 are both wide, passport-style foldables with a 7.6″ inner display, launched within weeks of each other. It is reasonable to wonder whether accessories cross over. They do not.
| Folded | iPhone Duo | Galaxy Z Fold 8 | Difference |
|---|---|---|---|
| Width | 84.1 mm | 81.9 mm | Duo 2.2 mm wider |
| Height | 117.8 mm | 123.9 mm | Duo 6.1 mm shorter |
| Thickness | 11.3 mm | 9.7 mm | Duo 1.6 mm thicker |
| Weight | 254 g | 201 g | Duo 53 g heavier |
Every one of those differences is far beyond what a case can absorb, before accounting for different camera layouts, button positions and hinge designs. A Z Fold 8 case on an iPhone Duo would be too narrow to fit around it and 6 mm too tall. No case, screen protector or camera protector transfers between the two.
Why fit is decided in fractions of a millimetre
On a conventional phone, a case that is slightly off still mostly works. On the iPhone Duo, four features make small errors visible.
- Two shells must agree. A Duo case is normally two pieces — one on each half. Both must sit correctly for the device to close and open smoothly, so an error in either one shows up at the fold.
- The fold leaves no room. With 0.9 mm between ideal and actual closed thickness, there is no slack for a shell that sits proud of the inner face.
- Thin walls flex less. A thin case cannot stretch to accommodate a dimension that is slightly off; it either fits or it rattles.
- The outer display protector adds a layer. A case lip that clears a bare screen may sit on the edge of a protector and lift it.
This is also why we have been clear across our guides that no third-party case from any maker has been verified on retail hardware yet. Every case available today was made from published dimensions and pre-release data. The measurements on this page are what case makers worked from; the retail units arriving on 23 October are what will confirm them.
The 8-point fit check for any new case
When your phone and case arrive, run through this before relying on the case — whichever brand you bought.
- 1. Fit the outer screen protector firstInstall it on the bare phone, then fit the case, so you test the real combination.
- 2. Close it and look along the edgeThe two halves should meet with no visible wedge or gap along the open side.
- 3. Open and close it ten timesThe motion should feel the same as without the case, with no catching or scraping at the spine.
- 4. Check the hinge area openNothing on the case should press into the inner display or sit across the fold line.
- 5. Press every buttonEach should click cleanly through the case, without needing extra force.
- 6. Check the camera openingThe lip should sit evenly around the lenses and not appear in the corner of photos.
- 7. Run a fingernail around the outer displayThe case lip should sit beside the protector's edge, not on top of it.
- 8. Shake it gently when foldedThere should be no rattle. A rattle means a shell is loose and will work further loose over time.
If a case fails any of these, contact the seller rather than forcing it. A case that stops the Duo closing flat is worse than no case.
Cases built around these dimensions
Magnetic Silicone Protective Case for iPhone Duo
$39.95
No ring, no pocket, no kickstand — nothing added on top of the wall thickness, so the folded profile stays closest to 11.3 mm of anything we sell. Ultra-thin aramid cases from other makers are thinner still, and we say so above.
Shop this case
Magnetic Hinge Protection Case for iPhone Duo
$49.95
Adds spine coverage over the shared hinge region without any hardware that raises one half. Keeps the outer display clear and the fold free of anything that could stop it closing flat.
Shop this case
3-Pack Outer Screen Protector for iPhone Duo
$19.95
Covers the 5.4″ outer display. Fit it first and run check 7 above with your case. We do not sell an inner-screen protector — that display's nano-texture finish should be left alone.
Shop the 3-packFrequently asked questions
What are the iPhone Duo's dimensions?
Folded: 84.1 mm wide, 117.8 mm tall and 11.3 mm thick. Open: 164.6 mm wide, 117.8 mm tall and 5.2 mm thick. It weighs 254 g.
How big is the iPhone Duo in inches?
Folded, about 3.31 × 4.64 × 0.44 inches. Open, about 6.48 × 4.64 × 0.20 inches. It weighs about 8.96 oz.
Is the iPhone Duo bigger than a passport?
No. Folded, it is 84.1 × 117.8 mm, smaller on both sides than a standard passport at 88 × 125 mm, though at 11.3 mm it is thicker.
How thick is the iPhone Duo with a case?
Typically about 13 to 15 mm folded, depending on the case. Ultra-thin cases add the least; wallet and kickstand cases add the most. Each case adds wall thickness on both outside faces when the device is folded.
How heavy is the iPhone Duo with a case?
Roughly 275 to 330 g, depending on the case. Ultra-thin aramid cases weigh around 20 g; wallet and kickstand cases weigh considerably more.
Do Galaxy Z Fold 8 cases fit the iPhone Duo?
No. Folded, the iPhone Duo is 2.2 mm wider, 6.1 mm shorter and 1.6 mm thicker than the Galaxy Z Fold 8, with a different camera and button layout. No case or protector transfers between them.
Why does the iPhone Duo open into landscape?
Because it is a wide foldable. Open, it is 164.6 mm wide and 117.8 mm tall. The folded and open shapes share the same 1.40 proportion, turned through 90 degrees.
How do I know if my iPhone Duo case fits properly?
Fit the outer screen protector first, then check that the phone closes with no gap, opens and closes smoothly, buttons click cleanly, the camera lip sits evenly, the case lip clears the protector's edge, and nothing rattles when folded.
Have iPhone Duo cases been tested on the real phone?
Not yet. The iPhone Duo ships on 23 October 2026, so no third-party case from any maker has been fit-tested on retail hardware. Cases available today were made from published dimensions and pre-release data.
Disclosure: This guide is published by Duo Case Co, which sells iPhone Duo cases. iPhone Duo dimensions and weight are from Apple's published specifications, labelled ✅ Confirmed; inch and ounce conversions are calculated. Bank card and passport sizes are the ISO/IEC 7810 ID-1 and ID-3 formats. Galaxy Z Fold 8 figures are from Samsung's published specifications. Competitor case thicknesses and weights are from each brand's published listing and have not been measured by us. Calculator presets are illustrative ranges, not measurements of specific products. No third-party iPhone Duo case, ours included, has been tested on retail hardware, because the device ships 23 October 2026. Duo Case Co is an independent accessories company and is not affiliated with, sponsored by or endorsed by Apple Inc. or Samsung Electronics. Apple, iPhone and iPhone Duo are trademarks of Apple Inc. Galaxy and Galaxy Z Fold are trademarks of Samsung Electronics.
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