A 20% tip is considered a generous and above-average tip in most situations.
It is commonly used as a benchmark for good service and is generally expected in upscale restaurants, where the service and quality of food are exceptional.
However, it's important to keep in mind that the size of the tip can vary based on several factors, such as the type of service received, the level of satisfaction with the service, and personal preferences.
Some people may choose to leave a smaller or larger tip based on these factors, and it's ultimately up to the individual to decide how much to tip.