Despite what feels like pressure to leave a gratuity wherever you go these days, what you choose to tip a waiter, barista, or bellhop is entirely up to your discretion. That means the "right amount" might look different from person to person and even occasion to occasion.

A recent nationwide survey found that Millennials and Gen Zers are much more consistent with tipping and more likely to leave a generous gratuity than Boomers. That same survey found that the people of Delaware are the best tippers, while Californians are, on average, the worst! But it's safe to say that all generations and geographic zones are experiencing tipping fatigue to some degree—whether they're acting on it or not. In two separate studies, 74% of respondents said tipping is out of control, while 59% claimed they have a negative view of tipping.

YouGov, meanwhile, found that 50% of people would "leave zero tip after receiving bad service." But is that...ethical? Socially acceptable? Or just a total a**hole move—no matter how fed up you are with tipping culture?

Etiquette expert and owner of the Protocol School of Texas Diane Gottsman says tipping is "not always necessary." However, these are very specific instances where this is true.

"The tipping app has caused many people to feel pressured and confused, so knowing when to tip and how much makes the decision more comfortable," she says. "There are some occasions when you may be offered the opportunity to tip and you can comfortably skip. For example, when you walk up to the counter and purchase a cup of coffee and you pay by credit card, and the app suggests multiple tip choices, along with a custom tip or no tip, consider it the same as a tipping jar. You can opt to tip, customize your tip, or hit the no tip button."

She makes one thing clear: It's pretty much never okay to leave without tipping at a sit-down restaurant—even if your service was poor. That doesn't mean you have to give 20% of your meal, but as Gottsman points out, there are typically "multiple people involved" in your dining experience.

"The protocol is to speak to the manager about the situation and let them know you’ve had a bad experience. More often than not they may adjust the cost of your meal," she explains. "You don’t have to leave a 20% tip, but you might want to leave 10 to 15% because there may be other people that share the tip and you don't want to penalize everyone."

If the service is good, Gottsman says a "fair and solid tip is 20%."

"There is wiggle room up and down but never less than 15%," she says. "For incredible service, or to show loyalty to a provider you use often, you can always leave more, depending on your budget and comfort level."

Lizzie Post, co-president of the Emily Post Institute and the great-great-granddaughter of the famous etiquette expert, agrees that leaving no tip at a sit-down restaurant is never acceptable.

“When you walk into a sit-down service restaurant—where you place an order with a server, they go and deal with it, they bring you food, they take that food away—that in our minds is non-negotiable. You leave a tip no matter what, even if it was the worst service you’ve ever had in your life," she told The Washington Post.

She also advocates for letting the manager know things weren't up to snuff. “You might learn a couple things as to why things were that bad, and that restaurant probably should have alerted folks to say, ‘Hey, we’re down a chef tonight. Things are going to be a little slow.’”

While the new research regarding tipping fatigue (and the response to it) might come as a surprise to some, this isn't the first time we've heard of it. In fact, 75 percent of Americans have expressed frustration over credit card machines in restaurants and tablets that automatically prompt tipping. Additional data reports that 65 percent of tips are given solely to avoid uncomfortable interactions and stare-downs from service workers.

This confusion over tipping etiquette is "precisely why we need One Fair Wage," according to Saru Jayaraman, the president and co-founder of One Fair Wage, a group that works to eliminate the tipped minimum wage across the U.S.

"Besides the fact that tips were always an incredibly unreliable source of income and subject to the whims and biases of customers, we are seeing a huge increase in 'tip fatigue' as more and more industries try to get the exemption the restaurant industry has,” Jayaraman told The Post.

"As tipping spreads as a result, customers tip less and less, with rising cost of living over the last few years, and it’s more and more important that workers receive a full minimum wage with tips on top."