Convert cubic feet per second to other values

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Flow rights expressed in cubic feet per second (CFS) are common in older water right claims.  The calculator on this page will convert CFS into the following volume/flow quantities:

  • GPS – gallons per second
  • GPM – gallons per minute
  • GPD – gallons per day
  • GPA – gallons per annum
  • AFA – acre feet per annum
  • MI – miners inches (see the discussion following the calculator, the values differ from state to state)
  • CFA – cubit feet per annum

Values used in the calculator.

  • 1 CFS = 7.4805 gps
  • 1 CFS = 448.83 gpm
  • 1 CFS = 646,316.883 gpd
  • 1 CFS = 235,905,662 gpa
  • 1 CFS = 50 MI *
  • 1 CFS = 40 MI *
  • 1 CFS = 38.4 MI *
  • 1 CFS = 723.97 AFA
  • 1 CFS = 31,536,000 CFA

* Different states use different values for miner’s inches.  See the discussion following the calculator.

How to use the calculator.

  1. Enter the number of AFA you wish to convert in the top of the form. DO NOT USE COMMAS.
  2. Select gpm, CFS, or CFM. (3) Click “Calculate. The converted expression will appear in the last box (conversion). If you selected CFS, the converted figure is an expression in CFS. To recalculate with a different expression (for example, gpm instead of CFS), be sure to select gpm, and click the calculate button again so that the math will reset.

To test the calculator, use 1 CFS. The results will match the formula above.

Total number of CFS
CFS Conversions

Notes about miner’s inches.

miner’s inch is not a measure of length, but it is the measurement of the rate of water flow in a miner’s sluice. Flow was measured by a hole one inch square with a head of one inch. Generally, one miner’s inch is a flow of 1.5 cubic feet per minute You will find references to “miner’s inches” in old water right filings and notices, as well as older decrees governing water rights.

As water demand increased with the development of large-scale mining technologies and the development of irrigation uses, the miner’s inch became an inadequate unit of measurement for flow rates, and was replaced by cubic feet per second.

A miner’s inch is not the same in all of the states:

State Number of miner's inches per CFS (cubic foot per second)
Idaho, Kansas, Nebraska, New Mexico, North Dakota, South Dakota ......50 miner's inches
Arizona, California, Montana, Oregon ......40 miner's inches
Other states ......38.4 miner's inches


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