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Apple Watch sizes are listed by case height in millimeters, not by screen diagonal. A 40mm Apple Watch is therefore not a 40mm-wide watch, and the 49mm Ultra is not a 49mm display.
Use the charts below to compare every Apple Watch case size in millimeters and inches, identify your model, and choose a compatible band.
Apple Watch case size chart
The first number in each row is Apple’s nominal case size. The dimensions that follow are the watch’s approximate height × width × depth.
| Case size | Nominal size | Actual dimensions (mm) | Actual dimensions (in) | Models |
|---|---|---|---|---|
| 38mm | 1.50in | 38.6 × 33.3 × 10.5mm | 1.52 × 1.31 × 0.41in | 1st generation, Series 1–3 |
| 40mm | 1.57in | 40 × 34 × 10.7mm | 1.57 × 1.34 × 0.42in | Series 4–6, SE, SE 2, SE 3 |
| 41mm | 1.61in | 41 × 35 × 10.7mm | 1.61 × 1.38 × 0.42in | Series 7–9 |
| 42mm, newer | 1.65in | 42 × 36 × 9.7mm | 1.65 × 1.42 × 0.38in | Series 10–11 |
| 42mm, older | 1.65in | 42 × 35.9 × 10.5mm | 1.65 × 1.41 × 0.41in | 1st generation, Series 1–3 |
| 44mm | 1.73in | 44 × 38 × 10.7mm | 1.73 × 1.50 × 0.42in | Series 4–9, SE, SE 2, SE 3 |
| 45mm | 1.77in | 45 × 38 × 10.7mm | 1.77 × 1.50 × 0.42in | Series 7–9 |
| 46mm | 1.81in | 46 × 39 × 9.7mm | 1.81 × 1.54 × 0.38in | Series 10–11 |
| 49mm | 1.93in | 49 × 44 × 12.0mm | 1.93 × 1.73 × 0.47in | Ultra, Ultra 2, Ultra 3 |
These are case measurements, not display measurements. The case height is measured vertically when the watch is viewed face-on; width runs across the wrist, and depth includes the body of the watch.
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Current Apple Watch sizes
Apple’s current U.S. lineup uses three case-size ranges:
| Current model | Available case sizes | Best description |
|---|---|---|
| Apple Watch Series 11 | 42mm, 46mm | Standard flagship model |
| Apple Watch SE 3 | 40mm, 44mm | Smaller and larger standard cases |
| Apple Watch Ultra 3 | 49mm | Largest, rugged case |
That means the familiar 41mm and 45mm sizes belong to older Series 7, Series 8, and Series 9 models, while 40mm and 44mm remain current through the SE 3. The latest standard Series models moved to 42mm and 46mm.
Apple Watch sizes by generation
| Apple Watch generation | Case sizes |
|---|---|
| Apple Watch, 1st generation | 38mm, 42mm |
| Series 1 | 38mm, 42mm |
| Series 2 | 38mm, 42mm |
| Series 3 | 38mm, 42mm |
| Series 4 | 40mm, 44mm |
| Series 5 | 40mm, 44mm |
| Series 6 | 40mm, 44mm |
| SE | 40mm, 44mm |
| Series 7 | 41mm, 45mm |
| Series 8 | 41mm, 45mm |
| SE 2 | 40mm, 44mm |
| Series 9 | 41mm, 45mm |
| Series 10 | 42mm, 46mm |
| SE 3 | 40mm, 44mm |
| Series 11 | 42mm, 46mm |
| Ultra | 49mm |
| Ultra 2 | 49mm |
| Ultra 3 | 49mm |
Apple Watch band compatibility by size
For most traditional Apple Watch bands, the useful compatibility groups are:
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| Band size group | Compatible case sizes |
|---|---|
| Small case group | 38mm, 40mm, 41mm |
| Large case group | 42mm, 44mm, 45mm |
| 46mm group | 44mm, 45mm, 46mm |
| 49mm Ultra group | 44mm, 45mm, 46mm, 49mm |
There is an important trap with the number 42mm. A 42mm watch from the first generation through Series 3 is in the older small-band family, alongside 38mm and 40mm watches. A 42mm Series 10 or Series 11 belongs to the newer large-case family and uses bands compatible with 44mm, 45mm, and 46mm cases.
Apple also says that bands made for 44mm, 45mm, or 46mm cases can fit a 49mm Ultra, and 49mm bands can fit 44mm, 45mm, and 46mm cases. The connector may fit, but the band can look different on a standard case and may not sit as neatly as a band designed for that watch.
Solo Loop and Braided Solo Loop sizing
Do not select a Solo Loop or Braided Solo Loop using case size alone. These bands are sized for wrist circumference, so you need both the compatible case group and the correct wrist measurement. Apple has changed its Solo Loop sizing guidance; use the current Apple sizing tool rather than relying on a previous Solo Loop size.
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How to find your Apple Watch size
From the paired iPhone
- Open the Apple Watch app on the iPhone.
- Tap My Watch.
- Go to General → About.
- Find Model Number.
- Tap the model-number field once. It changes from a part number beginning with M to a five-digit number beginning with A.
- Match that A-number with Apple’s official Apple Watch identification list.
From the watch itself
Turn the watch over and inspect the engraving around the rear sensor. Apple places the case-size information on the back of the watch. If the engraving is difficult to read, use the iPhone method instead of guessing from the screen or band.
What the millimeter number does—and does not—mean
- It is not the screen diagonal. A 45mm Apple Watch does not have a 45mm diagonal display.
- It is approximately the case height. The actual height can be slightly different, such as 38.6mm for the nominal 38mm case.
- It does not directly tell you wrist fit. Case size affects how large the watch looks, but band length and wrist circumference determine whether it fits securely.
- It does not identify every model by itself. The same 40mm size appears across several generations and SE models, and 42mm refers to two different band families.
Choosing between Apple Watch sizes
Choose the smaller case if you prefer a lighter, less prominent watch or have a narrow wrist. Choose the larger case if you want a larger viewing area, larger on-screen controls, or a more substantial appearance. The Ultra’s 49mm case is also considerably thicker—about 12mm—than current standard models, which are about 9.7mm or 10.7mm deep.
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For a used Apple Watch, confirm the exact generation as well as the case size. A replacement band, case protector, or screen protector that appears to fit by number alone may be wrong because Apple has changed case dimensions and band families over time.
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Official references
- Apple Watch identification and model-size list
- Apple Watch band compatibility
- Apple Watch Series 11 technical specifications
- Apple Watch SE 3 technical specifications
- Apple Watch Ultra 3 technical specifications
FAQ
Is a 40mm Apple Watch 40mm wide?
No. The 40mm label is the approximate case height. A 40mm case is about 40mm high, 34mm wide, and 10.7mm deep.
Which Apple Watch sizes use the same bands?
38mm, 40mm, and 41mm bands form one group. 44mm, 45mm, and 46mm bands form the main larger group, and 49mm Ultra bands are also compatible with 44mm, 45mm, and 46mm cases. Check the specific band listing before buying.
Are old 42mm and new 42mm Apple Watches the same size?
No. Older 42mm watches are from the 1st generation through Series 3 and use the 38mm/40mm/41mm band family. Newer 42mm watches begin with Series 10 and use the 44mm/45mm/46mm band family.
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How can I tell whether my Apple Watch is 40mm, 41mm, 42mm, or another size?
On the paired iPhone, open Apple Watch → My Watch → General → About, tap Model Number to reveal the A-number, and match it with Apple’s identification list. You can also read the case-size engraving on the back of the watch.
The Bottom Line
Apple Watch case sizes range from 38mm to 49mm. The current lineup is Series 11 at 42mm or 46mm, SE 3 at 40mm or 44mm, and Ultra 3 at 49mm. For bands, do not rely on the number alone—especially with 42mm models, where older and newer watches use different compatibility groups.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
