Cap gain calculation selling O/O home now a rental

[Eric Peterson]

I can't find an answer to this question anywhere with a search of the group. I have a specific question about how taxes will be calculated selling a home that was originally purchased as owner occupied and has been a rental for over 3 years. For example...

Home purchased in 2010 for $200,000

Owner lived in the home for 5 years

2016 converted to rental property. At the time the owner moved out the home was worth estimated $300,000.

2020 value if sold ~ $500,000

I know there will be other calculations (depreciation recapture, etc but for now I'm trying to keep the math simple. Is the capital gain calculated off $500,000- $200,000 = $300,000 or do you get to use an estimated step up value from when the home was converted which would be $500,000-$300,000 = $200,000?

Can anyone also point me to anything online that discusses this situation?