There are certain practices expected of people dining out: Don’t chew with your mouth open. Don’t blow your nose on the tablecloth. Don’t leave without paying the bill. And always leave a tip.

Most of this is manageable stuff, but restaurant tipping remains a slightly ambiguous practice. How much should you tip? What about when you’re getting take-out instead of table service?

Monica Burton at Eater thoughtfully crunched some numbers and solicited advice from service industry experts to come up with some answers. Sitting down for a meal at a restaurant almost always involves a 20 percent gratuity. (You can tip 15 percent, but it’s considered slightly stingy.) That should be 20 percent of the total taxed price, as well as factoring in any comped items. If your bill is $80 but your server waived a $20 dish for arriving a few minutes late, for example, you should tip for a $100 balance.  

Burton also covered the idea of penalizing servers for mistakes in their order. Unless you’ve been waiting an hour for food or your server is downright rude, it’s still good to tip 20 percent, as a lot of errors in food preparation or timeliness originate in the kitchen.

If the establishment has a built-in gratuity that’s pre-calculated and added in, you don’t need to leave any additional cash. That might feel weird, but it’s the restaurant’s choice.

Getting takeout? While your interaction with a server might be minimal, remember that the staff has packaged up your order, and that can actually take more time than if you were eating on the premises. (Think of sauces poured into separate containers.) Aim for 10 to 20 percent. Delivery? For most orders, $5 should suffice.

[h/t Eater]