Does 38mm band fit 40mm Apple Watch?

1. Apple watches are measured by height or display, not diagonal.
2. I think that I was confused by the numbers and the fact that they are selling both series 3 and 4 watches. The band that fits the 40 mm Series 4 will not fit the 44 mm Series 4, but the band that fits the 42 mm Series 3 will fit the 44 mm Series 4. Is that what you are saying?

Thanks

And yet at the Apple store they sell the same style/color in two models, one labeled for 40 mm and the other for 44 mm. And the specifications state that the 44 mm (high) watch is also 4 mm wider than the 40 mm (high) watch. And the band for the 44 mm watch is longer than the band for the 40 mm watch. But I’ll take your word for it if you’ve actually put a 42 mm band on a 44 mm watch and it fit.

I sense some confusion, because the watch size is described by the diagonal size of the display not the width of the band mounting channel. Apple simply used a thinner surround in the Series 4 so the active area is slightly wider in a case which is about the same size as the previous versions.

The 38mm and 40mm watches use the same (smaller) range of bands. The 42mm and 44mm Watches use the same (larger) bands.

I think you’re wrong about the case dimension because the convention since screens were first invented is to measure the diagonal, and at least in Series 3 the case dimension is 38.6mm and 42.5mm which should round up to the next integer with 39 and 43mm. However that is academic because you got the right idea about the crossover between earlier models and Series 4. Consider each range to have two variants, small case and large case, and bands come in two widths either small or large case compatible.

Actually, I'm right. Watch faces are measured differently than "screens". Google it. For example: "Unlike traditional watches, which measure case size horizontally, Apple measures the Apple Watch vertically. The smaller of the two watch sizes has a height of 38mm (specifically, 38.6mm); the larger, 42mm." You are correct that it does not matter for band measurments.

38mm and 40mm use the same watch bands

The 42mm and 44mm use the same band

If the 42 and 44 mm watches use the same band, why do you have to specify one size or the other when you order?

Being cynical about it, because there’s a box on the form and you can’t continue without filling the answer.

Yes.

38mm original, series 1, 2, and 3 watch bands all fit the 40mm Series 4

42mm original, series 1, 2, and 3 watch bands all fit the 44mm Series 4