I have tried a few rental property calculators and I'm looking for recommendations of some easy to use that I could use on my phone or desktop.

It's not free, but QB Desktop is the way to go, IMO.

Even doing comp itself is sometimes vague because like I say, comps high and comps low has three to four standard deviation, in a one million home, the range could be from $850k to $1.3mil.and to make even thing more complicated even the same house that was sold for X price in March, same house could go to 0.98x by December due to seasonality aspect of neighborhood and supply-demand dynamics.From statistical perspective, zEstimate is good when there're lot of similar comps in the neighborhood with condensed price pattern (for example, if neighborhood price is ranging from 200k-250k ; but it would be all over the place if home price is too low or too high).Even professional desktop appraisl would face similar problem as well, so I would not blame Zillow/zEstimate. this is merely statistical issue.So you still need professional appraisal.But again if you ask three different appraisar, they would come with three different opinions LOL , it's the reality.

If anyone else knows of one please let us know.There are a number of desktop software solutions.

Quickbooks is a better option (QBO or Desktop). 

@Courtney OldrinBelow are some tips/suggestions when it comes to organization / bookkeeping.Accounting Software Recommendations - Quickbooks(Desktop), Quickbooks(Online), Stessa, XeroOnline Storage to save receipts recommendations- Google Drive, Dropbox, Apple DriveExcel - to save information such as tenant name, lease start date, current rent, etc

Which version are your looking for QuickBooks Desktop or QuickBooks Online?

I don't diary miles (I should) but if I did I'd use Google Keep, an android note program that syncs with a desktop app. 

Do you use online or desktop?

Desktop version is the way to go.Thanks for sharing about Cozy.