Country
38mm / 40mm / 41mm Apple WatchS-M fits 125mm-165mm wristsM-L fits 145mm-190mm wrists
42mm / 44mm / 45mm / 49mm Apple WatchS-M fits 130mm-170mm wristsM-L fits 150mm-210mm wrists
All you need is a tape measure, and your wrist of course!
Step 1:
Use the millimetre (mm) side of the tape measure.