IWC Portofino

Most IWC Portofino references take a 18 mm watch strap: 111 of 294. The lug width follows the case size: 34 mm case → 18 mm, 37 mm case → 18 mm, 38 mm case → 20 mm and 45 mm case → 22 mm.

Shop 18 mm Shop 20 mm

IWC Portofino lug width by case size

294 references measured. Updated 2026-10-29.

Case	Lug width	References	Watch strap attachment	For example
29 mm	16 mm	19	—	IW3730-01, IW3730-02, IW3730-03
32 mm	18 mm	1	—	IW2010-01
34 mm	18 mm · 16 mm on 20 · 20 mm on 1	75	—	IW3331-03, IW3331-07, IW3513-01
35 mm	18 mm	9	—	IW3731-01, IW3731-02, IW3731-03
37 mm	18 mm · 20 mm on 2	44	—	IW4581-01, IW4581-02, IW4581-03
38 mm	20 mm	31	—	IW3533-01, IW3533-02, IW3533-03
39 mm	20 mm · 18 mm on 3	19	—	IW3563-01, IW3563-02, IW3563-03
40 mm	20 mm	26	—	IW3446-01, IW344602, IW3565-01
41 mm	20 mm	7	—	IW3590-01, IW3590-02, IW3783-01
42 mm	20 mm · 19 mm on 1 · 22 mm on 1	28	—	IW3910-01, IW3910-02, IW3910-06
44 mm	22 mm	1	—	IW5111-02
45 mm	22 mm · 18 mm on 2	32	—	IW5101-02, IW5101-03, IW5101-04
not recorded	20 mm · 22 mm on 1	2	—	IW4594-03

References that take a different watch strap

IW3564-02: 20 mm, not the 18 mm of most 34 mm cases
IW3574-01: 16 mm, not the 18 mm of most 34 mm cases
IW3574-03: 16 mm, not the 18 mm of most 34 mm cases
IW3574-04: 16 mm, not the 18 mm of most 34 mm cases
IW3574-05: 16 mm, not the 18 mm of most 34 mm cases
IW3574-06: 16 mm, not the 18 mm of most 34 mm cases
IW3574-08: 16 mm, not the 18 mm of most 34 mm cases
IW3574-09: 16 mm, not the 18 mm of most 34 mm cases
IW3574-10: 16 mm, not the 18 mm of most 34 mm cases
IW3574-11: 16 mm, not the 18 mm of most 34 mm cases
IW3574-12: 16 mm, not the 18 mm of most 34 mm cases
IW3574-13: 16 mm, not the 18 mm of most 34 mm cases
IW3574-14: 16 mm, not the 18 mm of most 34 mm cases
IW3574-15: 16 mm, not the 18 mm of most 34 mm cases
IW3574-16: 16 mm, not the 18 mm of most 34 mm cases
IW3574-17: 16 mm, not the 18 mm of most 34 mm cases
IW4598-01: 16 mm, not the 18 mm of most 34 mm cases
IW4598-05: 16 mm, not the 18 mm of most 34 mm cases
IW6576-01: 16 mm, not the 18 mm of most 34 mm cases
IW6598-01: 16 mm, not the 18 mm of most 34 mm cases
IW6598-02: 16 mm, not the 18 mm of most 34 mm cases
IW4581-18: 20 mm, not the 18 mm of most 37 mm cases
IW4590-14: 20 mm, not the 18 mm of most 37 mm cases
IW3592-01: 18 mm, not the 20 mm of most 39 mm cases

And 7 more in the full list below.

Questions about the IWC Portofino

Do all IWC Portofino case sizes take the same watch strap?

No. The lug width changes with the case size: the 34 mm case takes 18 mm, the 37 mm case takes 18 mm, the 38 mm case takes 20 mm, the 42 mm case takes 20 mm and the 45 mm case takes 22 mm. Check your case diameter before you buy.

Can two IWC Portofino watches with a 34 mm case take different watch straps?

Yes. Of the 75 IWC Portofino references with a 34 mm case, 54 take 18 mm, 20 take 16 mm and 1 take 20 mm. The reference number decides, not the case size alone.

Every IWC Portofino reference

Other IWC families

Inside each one the lug width often changes: it is the reference that decides.

All IWC families → · Why the size changes inside a family →