Watch strap compatibility

With one exception, all watch bands are compatible with all sizes of Apple Watch.

Change your Apple Watch band - Apple Support

38 mm, 40 mm, and 41 mm bands are all compatible with any Watch of the same size. (ex: using a 41mm Sport Loop band with a 38 mm Apple Watch Series 3.)

42 mm, 44 mm, and 45 mm bands are all compatible with any Watch of the same size. (ex: using a 42 mm Milanese Loop band with a 44 mm Apple Watch SE.)

The exception to this are the Solo Loop and Braided Solo Loop. These bands are one continuous stretchy band with no latch or clasp. They will likely fit all watches of the same size, but aren't tested or approved to work with Apple Watch Series 3 or earlier.

You don't need to measure your Apple Watch on your own. The size of your Apple Watch's watch face is engraved on the back of your watch.

This article can also help identify which model you have. Identify your Apple Watch - Apple Support