A 15% tip is generally considered the baseline for adequate service in the United States. It signals that the service met basic expectations. For excellent service, many diners choose to leave 18–20% or more.

A 15% tip is appropriate for standard sit-down restaurant service where everything went smoothly but nothing extraordinary stood out. It's also commonly used for takeout orders where some service is involved. For counter service or fast-casual dining, tipping is optional but 15% is a generous choice.

Find 10% of the bill by moving the decimal point one place to the left, then add half of that amount. For example, 10% of $50 is $5, and half of $5 is $2.50, so a 15% tip would be $7.50.