Knowing the size of your Apple Watch is essential for ordering new bands and accessories that fit correctly. But how do you determine the case size if you don’t remember which Model you originally purchased? There are a few easy ways to find out what size Apple Watch you have.
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Check the Engraving on the Back
Every Apple Watch case has a specific size engraved directly on the back. Look on the underside of your watch for a small engraving that states 38mm, 40mm, 41mm, 42mm, 44mm, 45mm, or 49mm. This number refers to the vertical height of the watch body, from top to bottom.
To read this tiny text, try taking a close-up picture with your iPhone and zooming in on the photo. Proper lighting also helps make the engraving more visible. Once you locate the measurement, you’ll know your exact Apple Watch dimensions.
Use the Watch App to Determine Apple Watch Size
You can also find your Apple Watch model number in the Watch app on your paired iPhone.
- Open the Watch app
- Go to the My Watch tab
- Scroll down and select General > About
- Look for the line labeled Model
Here is a handy list of Apple Watch model numbers and their corresponding case sizes:
| Model Number | Case Size |
| A1802, A1816, A1757 | 38mm |
| A2007, A2008, A2016, A2017, A2092, A2093, A2291, A2292, A2351, A2352 | 40mm |
| A2473, A2772, A2773, A2857, A2770 | 41mm |
| A1758, A1817, A1861, A1891, A1892, A1859, A1860 | 42mm |
| A1978, A1979, A2018, A2019, A2094, A2095, A2293, A2294, A2354, A2355 | 44mm |
| A2474, A2774, A2775, A2858, A2771 | 45mm |
| A2474, A2774, A2775, A2858, A2771 | 49mm |
So if your Apple Watch model starts with A2007, you have the 40mm size.
Measure Your Apple Watch with a Ruler (Series 5 Only)
Apple Watch Series 5 came in two Apple Watch sizes: 40mm and 44mm. If you have this Model, you can measure the case size directly with a ruler.
Place a ruler vertically against the side of your Apple Watch 5 case, from the top of the Digital Crown to the bottom edge. Read the measurement – it will either be around 40mm or 44mm tall.
Why Does Knowing Your Apple Watch Size Matter?
When purchasing replacement Apple Watch bands or certain accessories like screen protectors, you must order the size explicitly designed for your Apple Watch model.
For example, bands made for 42mm models will not correctly attach to the 38mm watches. And ill-fitting accessories can be uncomfortable to wear or not function properly with different Apple Watch sizes. So, take a minute to identify your Apple Watch size using one of the three methods above. Knowing the exact case dimensions will ensure accessories and bands are compatible and provide the intended fit.
You can quickly determine your Apple Watch size by checking the engraved measurement on the back, looking up the model number in your iPhone’s Watch app, or physically measuring a Series 5 model with a ruler.
With the proper case size identified, you can confidently shop for Apple Watch bands and accessories, knowing they will be a comfortable and secure match for your wrist.
