Yield / Interest rate calculation

Dear investors, 

I would like to open a debate about the calculation of interest on loans. Mintos suggests this formula: amount * number of days * (interest rate/360). However, this simple method often distorts the final interest that I received/will receive. 

How do you calculate future cash flows, interest and interest rates?

For cash flows, I have been using Excel, but the problem is that you have to manually copy the payment schedule and remove the currency sign. Perhaps Mintos should think about automatic Excel generation for this one too. 

Please share your opinions, thoughts and findings. Thank you!