Calculate how many gallons of water a shower uses from showerhead flow and minutes, with typical flow rates included, plus liters and household totals.

The average US shower runs about 8 minutes.

Household totals and water cost

Blank means 1. A decimal works as a daily average, e.g. 0.7.

Blank leaves out cost. Include sewer charges only if they are billed per the same volume.

Shower Water Usage Formula

The formula to calculate shower water usage is:

WU = FR × ST

Variables use compatible volume units. One U.S. liquid gallon is exactly 3.785411784 liters; see NIST Handbook 133, Appendix E. Imperial gallons are a different unit and are not supported here.

  • WU is water volume per shower in U.S. liquid gallons or liters
  • FR is the showerhead flow rate in U.S. liquid gallons per minute or liters per minute, matching the volume unit
  • ST is the time with water running, in minutes

Water volume equals flow rate multiplied by water-running minutes, assuming a constant or representative average flow. The inverse calculations are FR = WU / ST and ST = WU / FR; the divisor must be positive. A labeled flow rating is not an automatic measurement of your shower. EPA WaterSense explains showerhead performance under different water pressures.

What is Shower Water Usage?

Shower water usage is the volume used during a shower. Household daily volume equals volume per shower × people × showers per person per day. Blank optional people and frequency fields mean one person and one shower per person per day; a frequency of zero or a fractional average is allowed. Weekly, monthly and annual projections multiply daily volume by 7, 30 and 365 respectively. The month is a fixed 30-day estimate, not a selected calendar month.

How to Calculate Shower Water Usage?

Follow these steps to calculate your shower water usage:

  1. Pick a typical showerhead flow rate, or enter your own in U.S. liquid gallons per minute or liters per minute.
  2. Measure the time with water running (ST), in minutes.
  3. Use the formula WU = FR * ST to calculate the water usage (WU).
  4. Choose water used, flow rate or duration, then enter the other two quantities with compatible volume units.

Example Problem:

For a hypothetical example, assume a constant flow of 2.5 U.S. liquid gallons per minute with water running for 10 minutes. Use your own measured or appropriately rated flow rather than assuming this example applies to your shower.

Flow Rate (FR) = 2.5 U.S. liquid gallons per minute

Shower Time (ST) = 10 minutes

Water Usage (WU) = FR * ST = 2.5 * 10 = 25 U.S. liquid gallons, approximately 94.635 liters

The example uses 25 U.S. liquid gallons per shower. If a price is entered, estimated annual variable cost equals projected annual volume in the selected tariff basis ÷ 1,000 × the entered price. The tariff basis, per 1,000 U.S. gallons or per 1,000 liters, is separate from the display unit. Blank price omits cost; zero price produces zero cost. The result uses the currency of the entered tariff and excludes heating, fixed charges, taxes and any sewer charges not included in that tariff.