Apple Watch Series 5 comes in two screen sizes: 40mm and 44mm. The differing watch sizes give the 44mm a larger display area, a larger battery and of course a larger size sitting on the wrist. Otherwise, the features of both Apple Watch versions are the same.
Will it Sit Comfortably on My Wrist?
Buying an Apple Watch is not like buying a phone, it’s more like buying a pair of shoes. Choosing the larger size just to have a bigger screen may mean wearing something that turns out to be uncomfortable. Your Apple Watch is something you will be wearing all day so comfort is paramount. If you have a wrist circumference which is 15cm or less then you will almost certainly want to go with the 40mm. If you have a wrist size between 15cm and 16.5cm then you are probably in the goldilocks zone where you could comfortably choose either. If your wrist size is 16.5cm or above, then going with the larger 44mm version should still be comfortable but give you a larger screen display area.
Another factor here is how does it look on your wrist? Some people may simply prefer the appearance of a larger watch or a smaller watch. If you intend to have a mismatch between the size of your wrist and the size of your watch then you should definitely try each one on before buying. You need to make sure it is right for you both in terms of comfort and looks.
Do I Have to Match My Wrist Size?
No, but… wrist size is a big factor. Not only does it affect comfort levels but it also impacts the availability of suitable replacement Apple Watch bands. If you need to buy a replacement band or you simply would like to accessorise your Apple Watch with some new bands then you need to understand that the length of most bands available will correlate with the watch size. While not impossible, it’s certainly difficult to find both large bands for the 40mm and small bands for the 44mm. For example, if you have a 20cm wrist circumference and you purchase the 40mm Apple Watch, the number of Apple Watch bands you could find that fit both your wrist and your watch would be very small. Similarly, if you have a 13cm wrist circumference and choose the 44mm Apple Watch then you would be in a similar predicament.
Battery Life
So, your wrist size sits in the goldilocks zone and you still can’t decide. Battery Life is super important to most people and the 44mm Apple Watch has a 20% bigger battery than the 40mm model. Does this mean it will last 20% longer? No, it doesn’t. The 44mm also has 29% more pixels to power which offsets the larger battery. Apple reports both sized watches as having ‘up to 18 hours’ of battery life and does not specify longer battery life for either model. See here for further information on the battery testing Apple carried out.
Display Area
The 44mm is of course bigger, with a display area of 977 sq mm Vs 759 sq mm for the 40mm. This means text is a little bigger on the 44mm and you can fit a little more on the screen.

Source Apple
Price
In Australia you pay an extra $50 AUD for the larger 44mm all else being equal.
40mm | 44mm | |
---|---|---|
Display area | 759 sq mm | 977 sq mm |
Display size | 394×324 pixels | 448×368 pixels |
Entry-level GPS | $649 AUD | $699 AUD |
Entry-level Cellular | $799 AUD | $849 AUD |
Conclusion
If you’re still unsure, your best bet is to simply walk into a shop and try each Apple Watch size on. Most shops selling Apple Watches let you try them on first. If you can’t do that then you need to choose one that will sit comfortably on your wrist but also matches your style and personality! Otherwise, both are very similar in terms of features and price.