Apple Watch Series 4 is out now. And you can still buy last year’s Apple Watch Series 3, which is cheaper, unsurprisingly. So you’ve decided you want to buy an Apple smartwatch.

So, you may be asking, exactly what are the differences between last year’s Apple Watch Series 3 and the new one? Here are all the details that have changed,¬†how they matter and which model you should choose. I’ve broken things down into sections with conclusions in each one, which will help, I hope.


The new case is bigger than the old, measured according to the height.

  • Apple Watch Series 3 38mm GPS + Cellular: 38.6 x 33.3 x 11.4mm, 28.7g (aluminum). GPS only: same dimensions, 26.7g (aluminum)
  • Apple Watch Series 4 40mm GPS + Cellular: 39.8 x 34.4 x 10.7mm, 30.1g (aluminum), 39.8g (stainless steel). GPS only: same dimensions, 32.3g (aluminum)
  • Apple Watch Series 3 42mm GPS + Cellular: 42.5 x 36.4 x 11.4mm, 34.9g (aluminum). GPS only: same dimensions, 30.1g (aluminum)
  • Apple Watch Series 4 44mm GPS + Cellular: 44 x 37.8 x 10.7mm, 36.7g (aluminum), 47.9g (stainless steel). GPS only: same dimensions, 36.7g (aluminum).

That’s a slightly noticeable different size when you look at old and new side by side, but when you put the Watch on, it’s the thickness from front to back where you can feel the difference: in both cases the Watch has slimmed down by 0.7mm.

The new Watches are unsurprisingly a little heavier, and stainless steel is heavier than aluminum. Series 3 is only available in aluminum case and in Series 4, models with GPS but not cellular are also available in aluminum only.

If you want the lightest Watch, you’ll choose the GPS-only 38mm model but, frankly, the weight differences are scarcely noticeable when the Watch is on your wrist and there are more important considerations when choosing, I’d say.


  • Apple Watch Series 3 38mm: 340 x 272 resolution
  • Apple Watch Series 4 40mm: 394 x 324 resolution
  • Apple Watch Series 3 42mm: 390 x 312 resolution
  • Apple Watch Series 4 44mm: 448 x 368 resolution

Apple Watch Series 3 is great-looking with the same pin-sharp display found on earlier models, but Series 4’s display has changed beyond recognition. It’s not just because of the size of the display but the fact that the Series 3 display is rectangular and sits inside a reasonably wide bezel, while the Series 4 has a display which elegantly curves round at the corners, with a much narrower bezel around it.

In terms of display, Series 3 looks good, Series 4 is radically better. It’s worth noticing that the smaller Series 4 display is bigger than the larger Series 3 resolution. It’s one of the reasons the screen is such a striking change on the newest models.

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