How much do I save paying an extra $300 a month on my mortgage?

Starting from a typical $560,000 loan balance, here's what a consistent extra $300/month toward principal actually does to the payoff timeline.

This assumes the extra payment is made every single month for the life of the loan. Extra payments only help if they go toward principal — check with your lender that overpayments are applied that way, not held as a credit toward future payments.