How Extra Mortgage Payments Reduce Interest

A standard 30-year fixed mortgage is front-loaded with interest. In the early years, the vast majority of your monthly payment goes to interest — not to reducing your loan balance. On a $360,000 mortgage at 7%, your first payment of $2,395 sends roughly $2,100 to interest and only $295 to principal.

When you make an extra payment, that entire amount goes to principal. This immediately reduces the balance on which next month's interest is calculated — and every month after that. The savings compound over time because you're not just saving one month's interest; you're saving interest on that balance for every remaining month of your loan.

This is why even small extra payments early in a 30-year mortgage have an outsized effect. A $200 extra payment in month 1 doesn't just save $200 in principal — it effectively saves 29+ years of interest on that $200.

Let's take a concrete example: a $360,000 loan at 7.0% over 30 years.

Without extra payments: Monthly payment of $2,395. Over 30 years, you pay $502,200 total — meaning $142,200 of that is pure interest on top of the $360,000 borrowed.

With an extra $300/month: Your effective monthly payment becomes $2,695. The loan pays off in approximately 23 years and 4 months — saving 6 years and 8 months. Total interest paid drops from $502,200 to around $382,000 — a saving of roughly $120,000.

That extra $300/month costs you $84,600 over 23.4 years in additional payments, but saves $120,000 in interest — a net gain of around $35,400. And you own your home 6+ years sooner.

You don't have to increase your regular monthly payment. Many borrowers instead make one annual lump sum payment — from a tax refund, work bonus, or inheritance. The effect is similar.

On the same $360,000 at 7% example, adding one extra payment per year (equivalent to your regular monthly payment — a common strategy) saves approximately $86,000 in interest and cuts nearly 5 years from the loan term.

Some borrowers combine both strategies: a modest extra monthly payment plus an annual lump sum when funds are available. Use the Extra Payment Calculator to model any combination of monthly and annual additions.

This is the core personal finance question for homeowners with extra cash. Extra mortgage payments earn a guaranteed, risk-free return equal to your mortgage interest rate. At 7%, that's a guaranteed 7% return — better than most savings accounts or CDs.

Investing in the stock market has historically returned around 10% nominally (around 7% after inflation) — but with significant volatility and no guarantee. If your mortgage rate is lower, say 4–5%, the case for investing over extra payments becomes stronger.

For most people in 2024–2025 with mortgage rates above 6.5–7%, extra payments are a highly competitive use of funds — especially for risk-averse borrowers. The peace of mind of a shorter loan term and guaranteed interest savings is real and has genuine value beyond the numbers.

Many financial planners recommend a hybrid approach: max out tax-advantaged accounts (401k, IRA) first, then split any remaining surplus between investments and extra mortgage payments.

If increasing your payment feels complicated, consider switching to biweekly payments. Instead of making 12 monthly payments, you make 26 half-payments — the equivalent of 13 full payments per year. That one extra payment per year, applied automatically, typically saves 4–5 years and tens of thousands in interest on a 30-year mortgage.

Many banks offer biweekly payment programs. Be wary of third-party services that charge a setup fee to do this — you can replicate the effect simply by adding one-twelfth of your monthly payment to each month's regular payment.