How this calculator works
Water bills are usage × rate for water, often the same again for sewer, plus fixed charges. This estimates the usage from the number of people in your home and the average Americans use at home, converts it to the units your utility bills in, and prices it with the rates on your bill.
- Gallons = people × gallons per person per day × days in the billing period.
- Billing units = gallons ÷ 1,000, or gallons ÷ 748.05 when your utility bills per CCF (100 cubic feet; 1 cubic foot = 7.48 US gallons, NIST).
- Bill = units × water rate + units × sewer rate + fixed charges.
Worked example
With these inputs: people in the household 3; gallons per person per day 82; days in the billing period 30; your utility's rates are per 1,000 gallons; water rate $6; sewer rate $8; fixed charges $20.
The result is estimated bill for 30 days $123.32, with water used 7,380 gallons · 7.38 thousand gallons and water charge $44.28. Many utilities bill in tiers, charging more per unit as use rises. If yours does, use the rate for the tier you usually reach.
Where the 82 gallons comes from
The EPA's WaterSense program puts average home use at 82 gallons per person per day, from the US Geological Survey's national water-use estimates. Your household may use much more or less: lawn watering, a pool, older toilets or a leak push it up; efficient fixtures bring it down. Your bill shows actual use, so if you have one, divide the gallons by the days and the people and enter that instead.
Reading the rates on your bill
Most bills list a water rate and a sewer (wastewater) rate per unit, plus fixed charges such as a base or meter fee, and sometimes trash or stormwater. A CCF, also written HCF, is 100 cubic feet, or about 748 gallons. If the sewer charge is a flat fee rather than by use, enter 0 for the sewer rate and add the flat fee to the fixed charges.
Many utilities bill in tiers, where each unit costs more once use passes a threshold. Use the rate for the tier you usually land in, or work out an average rate from last month's bill (usage charges ÷ units).
Sources
Frequently asked questions
How do I calculate my water bill?
Multiply the units you used by the water rate, add the same for sewer if it's billed by use, then add the fixed charges. For three people at 82 gallons a day for 30 days, with $6 and $8 per 1,000 gallons and $20 fixed, that's $123.32.
How many gallons of water does a person use per day?
About 82 gallons at home on average in the US, according to the EPA's WaterSense program citing USGS data. It varies a lot with fixtures, habits and outdoor watering.
How many gallons are in a CCF?
About 748. A CCF is 100 cubic feet, and one cubic foot is 7.48 US gallons.
Why is my sewer charge higher than my water charge?
Treating wastewater often costs a utility more than supplying water, so many set a higher sewer rate. Some base sewer on winter water use so summer lawn watering doesn't count.