For a $100 bill at a full-service restaurant, the commonly cited 15% to 20% range works out to $15 to $20, though this can shift based on service quality and regional norms. Some people round to a clean number, like $20, for simplicity. This standard mainly applies to full-service, sit-down dining rather than counter service or takeout. A tip calculator can help you quickly see amounts at different percentages.

The percentage guideline itself generally doesn't change based on bill size; the same 15% to 20% range commonly applies whether the bill is $20 or $100, since the tip is meant to reflect a percentage of the service value rather than a flat amount. Some people do consider tipping a slightly lower percentage on very large bills for big groups, especially if an automatic gratuity has already been added, in which case an additional tip typically isn't expected. It's worth double-checking your receipt for an included service charge before adding another tip on a large bill. In general, applying the standard percentage range consistently is the more common approach.

Bar tipping in the U.S. often follows a somewhat different convention than restaurant table service; some people tip a smaller flat amount per drink for quick counter service, while others apply a percentage similar to restaurant dining for table service at a bar with waitstaff. For a larger bar tab like $100, applying a percentage similar to restaurant norms, 15% to 20%, is a common and reasonable approach, particularly if you were served at a table. Local and venue-specific norms can vary, so it's worth being attentive to context. When unsure, defaulting to the standard restaurant-style percentage range is generally a safe choice.

Many restaurants automatically add a service charge or gratuity, sometimes 18% to 20%, for large parties, in which case an additional tip is typically not expected unless you want to reward exceptional service further. It's important to check your receipt carefully, since paying both an automatic service charge and a separate full tip means over-tipping relative to standard custom. If no service charge was added despite being in a large group, tipping within the standard 15% to 20% range is generally appropriate. When in doubt, asking your server directly whether gratuity is included is a straightforward way to clarify.