There is no standard size for a glass of water. The amount in a "glass" can vary greatly.

Here are some common approximations:

* 8 ounces: This is often used as a general guideline, especially for measuring water intake.

* 12 ounces: Some glasses are larger and hold closer to 12 ounces.

* 16 ounces: This is considered a "large" glass and may be more common in restaurants or with specific glass types.

It's best to use a measuring cup to accurately determine the amount of water in a glass.