There’s a lot of complication for drips, especially with different plants in the same zones. I think I actually have my Rachio tuned in pretty well now, maybe this will help you. I have two drip zones, both with trees, shrubs and some other stuff. I’m not as worried about the other stuff so I made a spreadsheet calculating only the estimate for trees and shrubs separately, then combined/averaged them together for the whole zone. That’s the part that you can’t ever get 100% correct since every plant is different.
I don’t use emitters on my lines, just wide open 1/4" to each plant. My flow rate per plant is about 15 GPH. However, I remade an example in my spreadsheet for use with emitters, here’s a pic:
For example, emitters at 5 GPH per tree and 2 per shrub, then add them up. My zone 7 with 7 trees (35 gph) and 16 shrubs (32 gph), total GPH comes to 67. I did the area in sq ft, I’m not sure yet if that’s the accurate way to do the area for this but it seems to calculate the watering amount and time pretty close to what I used to do before Rachio. For the area, I did 25 sq ft per each shrub and 100 sq ft for each tree then added them up. You could get a lot more specific with that per plant if you want.
So to get the nozzle inches per hour, ((GPH * 231) / area ) / # of drips or emitters. The 231 is how many cubic inches per hour there are per GPH. So for my zone 7 it would be: ((67 * 231) / 1100 ) / 23 which equals 0.6 nozzle inches per hour. Then when setting crop coefficient and root depth its just a educated guess based on your plants. Calculating how many days between watering and water per application can help with that guess. You can use a spreadsheet to do that or create a flex schedule and see what Rachio sets it as on the calendar as well as the recommended watering time.
My spreadsheet pic is probably over complicated looking lol 