The best way to tell is by asking the manufacturer of the knife. As a general guide, European/American knives manufactured before 2010 have 20 degree edges while Asian style knives have 15 degree edges.
Thereof, are Wusthof knives 15 or 20 degrees?
On Wüsthof European-Style knives, the blade edge angle has been reduced to 28 degrees (14 degrees per side), while Asian-style Santoku, Nakiri and Chai Dao knives have a blade edge angle of 20 degrees (10 degrees per side).
Just so, can you sharpen a 20 degree knife to 15? Thus, if you change their angle from 20 degrees to 15, they will require more frequent sharpening. (Japanese knives are made from a harder, more brittle steel that holds a narrower edge for longer.) What’s more, you will inevitably end up removing a considerable amount of metal from your knife over time.