The iPhone Duo is Apple’s first foldable iPhone, and it is really two sizes in one phone. Closed, it is a short, thick slab you can hold in one hand. Open it up, and it becomes a wide, thin device with a 7.6-inch screen inside.
In this guide, you will find the iPhone Duo dimensions in both states — open and closed — in inches, centimetres and millimetres, its exact weight, and the size of both screens, so you can picture its real size before you buy it.
iPhone Duo Dimensions at a Glance
| Measurement | Open | Closed |
|---|---|---|
| Height | 4.64 in (11.78 cm / 117.8 mm) | 4.64 in (11.78 cm / 117.8 mm) |
| Width | 6.48 in (16.46 cm / 164.6 mm) | 3.31 in (8.41 cm / 84.1 mm) |
| Thickness | 0.20 in (0.52 cm / 5.2 mm) | 0.44 in (1.13 cm / 11.3 mm) |
| Inner display | 7.6 in OLED (1878 x 2670, 430 ppi) | – |
| Outer display | – | 5.4 in OLED (1398 x 2034, 460 ppi) |
| Weight | 8.96 oz (254 g) | 8.96 oz (254 g) |
Quick tip: The height stays 117.8 mm in both states — the fold changes width and thickness, not height. Folded, the phone is about half as wide and more than twice as thick as it is when open.
How Big Is the iPhone Duo When Open?
Open, the iPhone Duo measures 164.6 mm wide and 117.8 mm tall — 6.48 inches by 4.64 inches. That makes it wider than an iPhone 18 Pro Max is tall: the Pro Max stands 163.4 mm high, so the open Duo is 1.2 mm wider than the Pro Max is tall.
In the hand, the open Duo feels more like a small tablet than a phone. The 7.6-inch inner display is the main reason to open it — for reading, watching video and working with two apps side by side, the extra width is the whole point of the fold.
How Big Is the iPhone Duo When Closed?
Closed, the iPhone Duo measures 84.1 mm wide and 117.8 mm tall — 3.31 inches by 4.64 inches. It is a short, thick slab: shorter than most modern phones, and easy to grip in one hand.
Its footprint is smaller than a passport. A standard passport measures about 125 mm by 88 mm, so the closed Duo is shorter (117.8 mm against 125 mm) and narrower (84.1 mm against 88 mm) than a passport. The 5.4-inch outer display handles quick tasks — calls, messages and notifications — without opening the phone.
How Thick Is the iPhone Duo?
Thickness is where the two states differ most. Open, the iPhone Duo is just 5.2 mm thick (0.20 inches) — thinner than the iPhone 18 Pro Max, which is 8.75 mm thick. Unfolded, it is one of the thinnest iPhones ever made.
Closed, it is 11.3 mm thick (0.44 inches) — more than twice its open thickness, and 2.55 mm thicker than the iPhone 18 Pro Max. That is the trade-off of the fold: two thin halves stacked together make a noticeably thick closed phone.
How Much Does the iPhone Duo Weigh?
The iPhone Duo weighs 254 grams (8.96 ounces), the same in both states, since folding does not change its weight. That is just over half a pound — about the weight of a small paperback book, or a can of soup.
It is 5 grams heavier than the iPhone 18 Pro Max, which weighs 249 grams. On the published figures, that makes the iPhone Duo the heaviest iPhone to date, though the difference from the Pro Max is small enough that you would be unlikely to feel it in the hand.
iPhone Duo vs iPhone 18 Pro Max: Size Comparison
| Feature | iPhone Duo (open / closed) | iPhone 18 Pro Max | Difference |
|---|---|---|---|
| Display | 7.6 in inner / 5.4 in outer | 6.9 in | 0.7 in larger open |
| Height | 4.64 in (117.8 mm) both states | 6.43 in (163.4 mm) | 1.79 in shorter |
| Width | 6.48 in (164.6 mm) open / 3.31 in (84.1 mm) closed | 3.07 in (78.0 mm) | 3.41 in wider open / 0.24 in wider closed |
| Thickness | 0.20 in (5.2 mm) open / 0.44 in (11.3 mm) closed | 0.34 in (8.75 mm) | 0.14 in thinner open / 0.10 in thicker closed |
| Weight | 8.96 oz (254 g) | 8.78 oz (249 g) | 0.18 oz (5 g) heavier |
The two phones are built for different things. The Pro Max is a tall, single-screen phone; the Duo is a folding phone that is shorter and wider when open, and shorter and thicker when closed. Open, the Duo gives you a bigger screen than the Pro Max. Closed, it gives you a smaller footprint — but a thicker pocket.
Does the iPhone Duo Fit in Your Pocket?
Closed, yes, for most regular trouser and jacket pockets. At 3.31 inches wide and 4.64 inches tall, the closed Duo slides into a standard pocket, though at 0.44 inches thick it will fill it more completely than a slim phone. In tight jeans pockets it may feel snug when you sit down, so a jacket pocket or bag is more comfortable for all-day carrying.
Open, no — at 6.48 inches wide, the open Duo does not fit a normal pocket. Fold it closed before putting it away.
Everyday Size Comparisons
- Wider open than the Pro Max is tall (the open Duo is 6.48 inches wide; the iPhone 18 Pro Max is 6.43 inches tall).
- Closed footprint smaller than a passport (the closed Duo is 3.31 x 4.64 inches; a passport is about 3.46 x 4.92 inches).
- Open screen like a small tablet (the 7.6-inch inner display is close to a small tablet screen, in a device that folds shut).
- Closed height shorter than a dollar bill (the closed Duo is 4.64 inches tall; a US dollar bill is 6.14 inches long).
- About half a pound (at 8.96 ounces, just over half a pound, similar to a small paperback).
Frequently Asked Questions
How big is the iPhone Duo when folded?
Closed, the iPhone Duo measures 84.1 mm wide, 117.8 mm tall and 11.3 mm thick — 3.31 x 4.64 x 0.44 inches.
How big is the iPhone Duo when unfolded?
Open, it measures 164.6 mm wide, 117.8 mm tall and 5.2 mm thick — 6.48 x 4.64 x 0.20 inches.
How thick is the iPhone Duo?
It is 5.2 mm (0.20 inches) thick when open and 11.3 mm (0.44 inches) thick when closed. The iPhone 18 Pro Max is 8.75 mm thick, so the Duo is thinner open and thicker closed.
How much does the iPhone Duo weigh?
It weighs 254 grams (8.96 ounces) in both states — 5 grams more than the iPhone 18 Pro Max (249 grams).
What are the iPhone Duo screen sizes?
The inner display is 7.6 inches (OLED, 1878 x 2670, 430 ppi) and the outer display is 5.4 inches (OLED, 1398 x 2034, 460 ppi).
Conclusion
The iPhone Duo measures 164.6 x 117.8 x 5.2 mm when open and 84.1 x 117.8 x 11.3 mm when closed, and weighs 254 grams, with a 7.6-inch inner display and a 5.4-inch outer display. It is wider than an iPhone 18 Pro Max is tall when open, smaller than a passport when closed, and just 5 grams heavier than the Pro Max.
If you want the biggest screen in the smallest closed footprint, the Duo’s fold is worth it. If you want the thinnest phone in your pocket all day, the Pro Max — at 8.75 mm thick and 249 grams — will feel slimmer when closed.
Related Guides
- Xiaomi 18 Pro Dimensions: Size, Display and Weight Explained
- Vivo X500 Pro Max Dimensions: 6.85-Inch Display Size Guide
- How Big Is a 65-Inch TV? Dimensions, Width & Height Guide
Hi, I’m Michael Carter, I write simple, everyday size guides so you can picture any measurement in seconds.