So I made a Steem Power Interest Calculator (it calculates both compound and simple interest)
I used @dan 's wallet info and gain in Steem Power to get the average rates, so it may be a little different from your gains.
To improve the calculator you can give me info about your actual gains in specific time periods.
Eg: Gained 5 Steem Power in extactly 6 hours using 3017 Steem Power
The gain and time can be according to you.
And please Upvote if you found the tool useful.
Here is the Calculator.
I have also made a Steem Dollar Interest Calculator.