Overpayment calculator

strawb_shortcake

I may soon find myself in a position to pay 10% a year off my mortgage for this year and the remaining 3 years of the term. Where can I find a calculator that will show me what my balance will be at the end of the term?
If this comes to fruition, we could in theory pay the mortgage off, however; with the mortgage being affordable and us having minimal savings we are erring towards overpayment, the remainder would leave us with an emergency fund that could last approx 3 years though we may use some of that for much needed home improvements.
I'm sure I've used such calculator before but can't find t now.

TIA

[Deleted User]

Here?

https://www.google.com/search?source=hp&ei=HZ4jXcCtC8KblwT0-IywBA&q=mortgage+overpayment+calculator

strawb_shortcake

Thank you ��