Click on the link with the compatible excel for your computer and enable editing on the bar at the top. Choose meter type, type in Field Name and click on Make Field. At the bottom of the screen is a tab with the Field Name you just entered. Click on that and it will take you into the calculator sheet.
UNL link to simple version: http://cropwatch.unl.edu/irrigationmetercalculator
Water Meter Calculator App
This University of Nebraska-Lincoln Extension iPhone app will help irrigators calculate the amount of water pumped by their irrigation pumping plant.
The Water Meter Calculator App allows the user to store data, such as field size in acres, flow meter units and allocation and annual irrigation caps for each field.
The app is available for download at the Apple App Store for $1.99. It is also available in the Google Play store.