How do I measure the size of my watch band
How do I measure my wrist for my watch band size?
Question marked as
Top-ranking reply
I have to guess you are considering one of the single-piece non adjustable bands like Solo Loop where correct length is a critical measurement. Go to the online Apple Store (Buy Apple Watch Bands - Apple) and find the band which interests you, and you should see a section describing how to determine the correct size.
If you are simply concerned about the correct width for the band and watch case size this is also described.
Band Compatibility
You can match most bands with any Apple Watch Series 3 or newer case of the same size. The 41mm bands work with 38mm and 40mm cases; the 45mm bands work with 42mm, 44mm and 49mm cases.
The Solo Loop and Braided Solo Loop bands are only compatible with Apple Watch SE and Apple Watch Series 4 or newer. The 40mm and 41mm cases work with band sizes 1–9; the 44mm and 45mm cases works with band sizes 1–12.