Interest only loan vs fixed loan saving

[Edward Mccracken]

I don't feel smart asking this question but I have 7, interest only loans that are amortized over 20 years at 6.5% on a 10 year balloon. I'm currently into year 2. Actually, I'm 7 years into the loan but they just renewed me 2 years ago for these terms. Now, these terms might not be the best but 7 years ago NO ONE would give loans like this. I would essentially go into these properties rehabbed and rented for no money down and good cash flow.

I can not find any where on the internet a calculator on how these loans work. I'm trying to figure out if I should seek someone with private money to refinance me for a 20 year fixed around the same terms for interest. I'm sure I will save money but I just cant figure it out on paper.

I wanted to pay off my two biggest mortgages with them, which are 35k and 50k. The 35k is worth 50k and the 50k is 85k. 

The math that I'm doing doesn't show that I'm saving that much buy switching over to a fixed loan.

Please tell me I'm wrong and I should try and refi these loans...