Pay Off a 15-Year Mortgage Early — How Extra Payments Save Even More

The 15-year advantage you already have

Choosing a 15-year mortgage over a 30-year is already one of the best financial decisions a homeowner can make. The rate is lower (typically 0.5-0.75% less), the term is half, and the total interest is roughly 60-65% less. On a $300,000 loan, that translates to about $261,000 in savings compared to a 30-year term.

But even with those advantages, a 15-year mortgage at 6.25% still costs you $158,000 in interest on $300,000 borrowed. That's not nothing. Extra payments chip away at that remaining cost — and because the amortization schedule is already front-loaded toward principal (compared to a 30-year), every extra dollar goes further.

What overpaying a 15-year mortgage saves — real numbers

Here's the complete picture for a $300,000 loan at 6.25% over 15 years (base monthly payment: approximately $2,568):

$300/month extra brings you from 15 years to 12. That's three more years of your life without a mortgage payment — and $22,000 that stays in your account instead of going to your lender. At $1,000/month extra, you'd be mortgage-free in about 8 years. Consider what that means: buying a home and owning it outright before your kid finishes middle school.

15-year vs 30-year: the total cost comparison

People sometimes wonder whether they should have gone 15-year in the first place, or picked a 30-year and overpaid. Here's the comparison on $300,000:

The 15-year costs $572 more per month. But it saves over $260,000 in total interest. That's roughly $17,350 saved per year of the shorter term. No other routine financial decision delivers that kind of return. The mortgage amortization guide explains why the interest structure works this way.

When overpaying a 15-year loan makes the most sense

Your rate matters. At 6-7%, overpaying a 15-year mortgage delivers a strong guaranteed return — your effective return equals your interest rate, risk-free. That competes with or beats after-tax stock market returns for most people.

At rates below 4% (which some borrowers locked in during 2020-2021), the calculus shifts. A guaranteed 3.5% return from overpaying is solid, but many investment options deliver more over the same time horizon. If you have a sub-4% 15-year mortgage, the case for investing instead of overpaying is reasonable.

But there's something the pure math doesn't capture: the psychological value of being debt-free. Paying off your home 3-5 years early doesn't just save interest — it fundamentally changes your financial flexibility and stress levels. For many people, that peace of mind is worth more than the marginal investment return difference.

Practical tips for 15-year overpayers

Since you're already making a substantial monthly payment (~$2,500+ on a $300,000 loan), your extra payment budget may be more limited than a 30-year borrower's. That's fine. Even $100/month saves over $8,000 in interest on a $300,000 loan.

A smart approach: commit to directing any raises, bonuses, or windfalls to extra principal payments. If your income increases by $200/month next year, split it — $100 to lifestyle, $100 to the mortgage. You won't feel the pinch, and the compounding effect over the remaining term is significant. For a detailed comparison of monthly vs lump-sum overpayment approaches, the lump sum vs monthly overpayment guide has the full breakdown.

For current 15-year mortgage rate data, Freddie Mac's Primary Mortgage Market Survey tracks weekly averages. For the full regulatory picture on prepayment rights, the CFPB homeowner guide covers consumer protections.