Using ounces as a standard unit of liquid volume for comparison, there are 8 ounces in a glass and 33.81 ounces in 1 liter. Then divide 33.81 by 8, for 4.23 glasses in 1 liter.
It is often easier to convert between two different units of measure by using a third unit that is more commonly used in calculations. For liquid volume, the two main standard units are ounces and milliliters. In this case, ounces are used due to the relative ease of converting glasses into ounces instead of using milliliters. Consider that one glass equals 236.59 milliliters and using a calculator makes conversions more practical.