The loan simulator amortises every loan you have recorded — home, car, education, personal, or an interest-only loan from family — and runs them forward together. Put in what you could pay extra each month and it shows when you would be clear and how much interest is never charged.
It also runs backwards: name the month you want to be debt-free by and it works out what that costs a month, counting instalments freed by loans that close along the way.