Carb Manager has a basic version that is 100% free, and always will be. There is never any cost to use the Carb Manager free version. In fact, the majority of our users are on the free membership plan!
We do offer a Premium plan, which costs $8.49/month or $39.99 for a full year. Users on the free plan can and will see prompts in the app that encourage them to upgrade to the paid Premium plan, but that's always optional.