Apple Watch Series 6 and Series 3 bands are exclusively compatible with Apple Watch Series 4 and newer models.
Apple Watch fans who still own Series 6 or Series 3 watches have plenty of strap options. Many Series 7 watches are too big for Series 3 straps, which have a 3 mm difference in size from Series 7 watches.
Since Apple increased the size of the Apple Watch case without altering the strap sizes, your 38mm Apple Watch Series 6 bands will fit your 40mm Apple Watch. All watch straps are compatible with all watch series and editions.
Apple didn't alter the strap sizes when they expanded the Apple Watch case a little bit, so if you have a 38mm Apple Watch, your straps will still fit the 40mm Apple Watch Series 6. All watch series and editions are compatible with all strap sizes and shapes.
The connector on all Apple Watches is the same size and shape. The 38mm straps fit the 40mm watches.
Smaller watches (38mm and 40mm) use the same strap range (smaller). The 42mm and 44mm watches use the same (larger) straps.
The Apple Watch Series 4 has been updated to a new size (40mm and 44mm rather than 38mm and 42mm), and the older bands will fit the newer ones.
You cannot connect a 38mm strap to a 44mm watch. The Apple Watch Series 3 has two display sizes, 42 mm and 44 mm, but they keep the same strap mounting slots. Furthermore, both 38 mm and 40 mm screens have smaller display sizes.
The 40mm Apple Watch Series 3 has a slightly larger display than the 38mm Apple Watch Series 3, although the screen is much bigger.
The Apple Watch's interchangeable straps let you change them up for different styles at any time. Apple Watches have smaller wallets and wrists than most other models. It is not possible to connect an Apple Watch band to a standard watch band.
Third-party options may be available in the future, as Apple uses its own proprietary system to connect the band.
The bands for Apple Watch Series 1, 2 and 3, Apple Watch Series 4 and Apple Watch SE are compatible with up to three band sizes: 38 mm, 40 mm, and 41 mm.
The cases of standard watches should range from 34 mm to 40 mm for females and from 40 mm to 46 mm for males. Because cases from 38 mm to 42 mm are now known as unisex sizes and are popular among those seeking a little less or a little more motion, those who want less or more motion will likely prefer them.
If you want to buy an Apple Watch strap, you should determine the size of your watch. Apple Watch Series 4 and later, Apple Watch Series 1, 2, and 3, and Apple Watch SE all use the same band size.
All Apple Watch Series 7 bands are compatible with the 38mm, 40mm, and 41mm case sizes. You must buy straps that match the size of your watch.
Even if a strap fits, it may not match the finish of your watch. Using a paper tool, tightly wrap the sleeve shape around your wrist, then secure the widest part with tape. If necessary, use some adhesive tape to keep the widest part in place. The tool should not slip or feel uncomfortable.
The arrows on your Apple Watch display inform you where to find your band number. There is no problem using a lot of watch bands if you have them. You can identify your band number by looking at the arrows.
You can use a larger Apple Watch band on the new 40mm Apple Watches, or an older 42mm band on the 44mm ones. The previous generation of wearables that were the larger size option of their kind are likely to work with the larger Apple Watch band.
It is encouraging for Apple consumers that the old watch bands fit the new Apple Watch Series 4 sizes (40mm and 44mm instead of 38mm and 42mm). It's also remarkable that Apple has taken the risk of losing these diehard fans by announcing that Series 7 and its collection of watch bands will offer only a single usable strap, given that the Series 7 is backward-compatible only as far as Series 4.
Apple Watch Series 6 and Series 3 bands are only compatible with the Apple Watch Series 4 and newer models. Apple Watch Series 6 and Series 3 bands are plenty for Apple Watch Series 6 and Series 3 owners, who can choose from a variety of straps.
Apple Watch Series 7 watches are often incompatible with Series 3 watches because the strap may be too small due to a 3 mm difference between the Series 3's 42-mm and Series 7's 45-mm straps.