The calculator on this page will convert miners inches into more commonly-used volume/flow quantities. The value of miners inches differs from state to state. See the discussion following the calculator.

This calculator will convert miners inches (using various state standards) into the following volume/flow quantities:

- CFS – cubic feet per second (Note – see the discussion on the various MI measurements used in different states; you will need to select the CFS option that applies to your state)
- GPM – gallons per minute *
- AFA – acre feet per annum *

* The calculator will ONLY calculate GPM and AFA based on the 1 MI = 40 CFS standard used in Arizona, California, Montana and Oregon. There is a workaround. If your state uses another value for miners inches, use the calculator below to calculate CFS, then use **the CFS calculator** to convert the cubic feet per second into GPM or AFA.

## Values used in the calculator.

- 1 MI = 11.22 gpm
- 1 MI = 0.020 CFS (or 1/50 CFS)
- 1 MI = 0.025 CFS (or 1/40 CFS)
- 1 MI = 0.026 CFS (or 1/38.4 CFS)
- 1 MI = 18.091 AFA

## How to use the calculator.

- Enter the number of miners inches you wish to convert in the top of the form. DO NOT USE COMMAS.
- Select GPM, CFS or AFA. (Note, for GPM or AFA, if your state uses another value for miners inches, use the calculator below to calculate CFS, then use
**the CFS calculator**to convert the cubic feet per second into GPM or AFA. - If you selected CFS, the converted figure is an expression in CFS. To recalculate with a different expression (for example, AFA instead of CFS), be sure to select AFA, and click the calculate button again so that the math will reset.

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

## Notes about miner’s inches.

A **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 |