Closed short and thick; open wide and thin
Duo is not a Pro Max that folds. Closed it sits like a short, thick passport phone; open it becomes a wide, thin sheet—so you need both sizes to judge the day-to-day.
Apple’s name for this phone is iPhone Duo. Nicknames like “18 foldable” or “flip” usually point to the same model.
Duo versus 18 Pro or Pro Max
Going by size and how you carry a phone:
- Lean Duo if: You want closed height at 117.8 mm (much shorter than Pro Max’s 163.4 mm), a wide cover you can thumb more easily, and a 7.6″-class inner screen when open—even if closed thickness is 11.3 mm and weight is 254 g.
- Stay on 18 Pro / Max if: You want a familiar tall slab, thinner closed feel (8.75 mm), lighter Pro mass (211 g), and no hinge. Pro Max is still the taller phone for video-first users who never fold.
Official size chart
Closed and open rows from Apple Tech Specs. Screen inches: cover when closed, inner when open.
iPhone Duo (closed)
- Size (mm)
- 117.8 × 84.1 × 11.3 mm
- Size (in)
- 4.64 × 3.31 × 0.44 in
- Screen
- 5.4″
- Weight
- 254 g
Pocket height win; 11.3 mm thick
iPhone Duo (open)
- Size (mm)
- 117.8 × 164.6 × 5.2 mm
- Size (in)
- 4.64 × 6.48 × 0.2 in
- Screen
- 7.6″
- Weight
- 254 g
Desk width; 5.2 mm thin
iPhone 18 Pro
- Size (mm)
- 150 × 71.9 × 8.75 mm
- Size (in)
- 5.91 × 2.83 × 0.34 in
- Screen
- 6.3″
- Weight
- 211 g
Everyday slab reference
iPhone 18 Pro Max
- Size (mm)
- 163.4 × 78 × 8.75 mm
- Size (in)
- 6.43 × 3.07 × 0.34 in
- Screen
- 6.9″
- Weight
- 249 g
Tallest slab here
| Model | Size (mm) | Screen | Weight | Quick note |
|---|---|---|---|---|
| iPhone Duo (closed) | 117.8 × 84.1 × 11.3 mm4.64 × 3.31 × 0.44 in | 5.4″ | 254 g | Pocket height win; 11.3 mm thick |
| iPhone Duo (open) | 117.8 × 164.6 × 5.2 mm4.64 × 6.48 × 0.2 in | 7.6″ | 254 g | Desk width; 5.2 mm thin |
| iPhone 18 Pro | 150 × 71.9 × 8.75 mm5.91 × 2.83 × 0.34 in | 6.3″ | 211 g | Everyday slab reference |
| iPhone 18 Pro Max | 163.4 × 78 × 8.75 mm6.43 × 3.07 × 0.34 in | 6.9″ | 249 g | Tallest slab here |
Duo sizes from Apple Tech Specs. Open thickness is the published body depth.
Closed: pockets and bags
Closed height 117.8 mm sits well below Pro (150.0 mm) and Pro Max (163.4 mm), so less of the phone peeks from a typical front pocket. That is the main “passport” advantage.
Trade-off: 84.1 mm width and 11.3 mm thickness are larger than Pro. Skinny jeans can feel tight; jacket and coat pockets usually feel better. At 254 g it is also heavier than 18 Pro (211 g).
Open: desk and lap width
Open width jumps to 164.6 mm—wider than Pro Max’s 78.0 mm body—while thickness drops to 5.2 mm. Height stays 117.8 mm, so the open sheet is short and wide, not Max-tall.
If you mainly want a bigger screen while still carrying a tall bar phone, Pro Max is simpler. If you want a near-tablet span that folds away, Duo’s open row is the point of the product.
Next to the Pro models
The front lineup makes the shorter closed Duo obvious; expand for closed and open reference sheets.
Closed and open reference views
Related sizes
Want slab-phone advice only? iPhone 18 Pro size guide · All phones