How to structure navigation with many similar items?

So I have an app on the google play store currently (https://play.google.com/store/apps/details?id=com.euandeas.RowerStuff) which has calculators in it for rowers. I currently have free essential calculators only, but plan to add some premium calculators later. I also plan to release a similar version for ios?

App
    Basic Calculators
        Pace
        Watts
        Weight
    Premium Calculators
        VO2
        Prediction

I dont want it all on one tab bar as that is to clustered and heard that hamburgers arent the best ideas, but I was thinking about having a home screen with cards that would navigate to each and separating them out with titles. What do you think I should use