The utility bill is made up of two components: a base charge and a consumption charge. If you receive City water and sewer services, you will have a base and a consumption charge for both services. If you have only one service, you will have only the appropriate base and consumption charge.
The base charge is a monthly minimum charge based upon the type and size of the metered service you have. Additionally, you are billed a consumption charge for the amount of water you use. Take a look at the usage number on your bill. Multiply that number by 1,000 to give you the amount of water (in thousands of gallons) you used.