Why small extra payments matter
Early in a mortgage, most of each payment is interest. An extra dollar of principal paid now stops interest from accruing on that dollar for the rest of the loan, so the savings compound. That is why paying an extra $100 to $300 a month in the first decade shortens a 30-year loan by years.
Specify principal-only on every extra payment, confirm there is no prepayment penalty, and keep your emergency fund funded first. Use the biweekly calculator if you prefer a paycheck-aligned approach.