How Extra Mortgage Payments Save Money

A practical method

An extra loan payment saves money when it is applied to principal because future interest is then calculated on a smaller balance. The effect depends on the remaining rate, balance, term, payment timing, and whether the lender keeps the scheduled payment unchanged or recasts the loan.

1. Confirm principal application: Tell the lender to apply the extra amount to principal rather than treating it as an early scheduled payment.
2. Check restrictions: Review prepayment penalties, minimums, and servicing rules before sending money.
3. Model the baseline: Calculate the existing payoff date and total remaining interest without extras.
4. Add the extra schedule: Compare monthly, annual, or one-time extra payments using the same starting date and balance.

Worked example

If an extra $100 reduces principal today, interest in every later period is calculated on a balance that is at least $100 lower. The exact lifetime saving is not simply $100 times the interest rate; it depends on how many periods remain and how the loan amortizes.

Checks, edge cases, and common mistakes

• Do not drain emergency savings solely to reduce a low-rate loan without comparing liquidity needs.
• Confirm whether the payment changes the term, the installment, or both.
• Account for any penalty or lost alternative return in the comparison.
• Use the lender's payoff statement for final contractual figures.