/ck/ - Food & Cooking

What is the average tip percentage when going out to eat?
I'm trying to create a system that creates tiers of how much I should tip given varying circumstances.

For instance the scale of the restaurant. Is it fine dining? Is it casual fast dining? Fast food? To-go pick up? Delivery?
I know the starting tip is 20% but what are some other factors that can make or break the tip?
Any of you coo/ck/s can help me?

Does anyone else on /ck/ do this already and can give me some pointers?

Thanks in advance!