Apple Watch Series 6
How do you get the option of Tip in the calculator as you mentioned it's not available in all regions? Is it not available in Asutralia?
Apple Watch Series 6, watchOS 7
Question marked as
Yes curiously enough and according to this, Use Calculator on Apple Watch - Apple Support the tip feature is not available in all regions.
However, check Settings on the Apple Watch itself. Under the Calculator there is a checkbox to change the percent button to Tip. Does that work for you?