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Water Bill Calculator

Enter your gallons used and rate to estimate your water bill.

How it is calculated

The bill has a fixed part and a usage part: usage charge = (gallons ÷ 1000) × rate per 1000 gallons and bill = base charge + usage charge. Gallons are US gallons, the rate is the price per 1,000 gallons from your tariff, and the base charge is the fixed monthly service fee (if you leave it empty, it counts as zero). The rate must be above zero; zero gallons gives just the base charge, and negative gallons give no result. The tool applies one flat rate to all usage: it does not model tiered or block pricing where the price rises with consumption, and it does not add a separate sewer charge, stormwater fee or tax unless you fold them into the base charge or the rate. If your bill shows cubic feet or cubic metres, convert to gallons first. Amounts are in US dollars.

Worked example

A household uses 6,500 gallons in a month. The utility charges 5.20 per 1,000 gallons and an 18.00 base service charge. Usage: 6,500 ÷ 1,000 = 6.5 thousand gallons, and 6.5 × 5.20 = $33.80. Bill: 18.00 + 33.80 = $51.80. The base charge makes up about a third of the bill here, which is why a month of very low use still produces a bill of 18.00.

Try this example →

Common mistakes

  • Entering the rate per gallon instead of per 1,000 gallons. A rate of 0.0052 per gallon must be typed as 5.20, otherwise the usage charge is a thousand times too small.
  • Using a billing unit other than gallons. Utilities that bill in hundred cubic feet (CCF) or cubic metres need the usage converted first (1 CCF is about 748 gallons).
  • Using one average rate when the utility has tiers. If the price per 1,000 gallons rises after a certain usage, a single flat rate understates a high-use month.
  • Leaving out sewer, trash or tax lines that appear on the bill. Add them to the base charge or the result will be lower than the real total.
  • Entering annual or quarterly usage with a monthly base charge. Keep the period of gallons and the base charge the same.

About this calculator

Most municipal water utilities bill in two parts: a fixed base service charge that covers meter and infrastructure costs regardless of use, plus a volumetric rate per 1,000 gallons (or per hundred cubic feet, CCF, in some areas) that scales with how much water actually passes through the meter. Total bill = base charge + (gallons used ÷ 1,000 × rate).

Homeowners use this breakdown to understand why their bill changed month to month, and property managers and landlords use it to estimate or allocate water costs across units before a bill arrives. Multiply the gallons on your meter by the rate per 1,000 gallons, add the fixed base charge, and you have an estimate of the bill before it arrives.

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Comments (1)

  • Editorial team

    If your utility bills in tiers, run the tool once per tier and add the results. Enter the base charge in the first run only and leave it blank in the rest, because blank counts as zero. As a reference, 6,500 gallons at 5.20 per 1,000 with an 18.00 base is 51.80 USD, and 12,000 gallons is 80.40 USD. A month with zero gallons shows just the base charge. How many tiers does your bill have?

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