Extra Mortgage Payment Calculator

Paying a little extra on your mortgage each month can take years off the loan and save tens of thousands in interest. This calculator shows exactly how much an extra payment saves, so you can compare it with other uses for the money.

What this calculator does

Enter your loan balance, interest rate, current principal and interest payment and the extra amount you'd pay each month. It shows:

• the interest you'd save,
• the time you'd save, and
• your payoff time with and without the extra payment.

The formula in plain English

Each month, interest is charged on the balance: balance × rate ÷ 12. Your payment covers that interest, and the rest reduces the balance.

An extra payment goes entirely to principal. A smaller balance means less interest next month, so more of every later payment reduces principal too.

The calculator runs the loan month by month with and without the extra payment and compares total interest and months.

A worked example

Dr. Thomas owes $400,000 at 6.4% on a new 30-year loan, with a principal and interest payment of about $2,503. She adds $300 a month.

• Without extra: 30 years.
• With extra: about 22.5 years.
• Time saved: about 90 months, or 7.5 years.
• Interest saved: about $145,600.

That's a guaranteed 6.4% return on every extra dollar, and she'll be mortgage-free years sooner.

Why it matters at each career stage

If you're: Resident / fellow

Extra mortgage payments are rarely a priority in training. Build an emergency fund and get any retirement match first.

If you're: Employed

After maxing out retirement accounts and paying off higher-rate debt, extra mortgage payments are a reasonable choice, especially if your rate is above about 5% or you value being debt-free before retirement.

If you're: Practice owner

Business owners often need cash for the practice. Keep enough liquidity before sending extra money to a mortgage, because home equity is hard to access quickly.

Paying extra vs investing

Your rate matters. At 3%, investing likely wins over time. At 7%, paying down the mortgage is a strong, risk-free return.

Taxes matter. Mortgage interest is deductible only if you itemize, which many people no longer do. Retirement contributions often have bigger tax benefits.

Flexibility matters. Money in an investment account is easier to reach than home equity.

Peace of mind matters. Being mortgage-free before retirement lowers your required income and stress.

Ways to pay extra

Monthly extra. Add a fixed amount to each payment.

Lump sums. Apply bonuses or tax refunds.

Biweekly payments. Pay half every two weeks for one extra payment a year.

Round up. Round your payment up to the next hundred.

Whichever you choose, ask your servicer to apply extra payments to principal and check your statements.

A simple way to decide

Many people split the difference: they keep investing in retirement accounts for the tax benefits and long-term growth, and send a modest fixed amount to the mortgage each month. As retirement gets closer, they shift more toward the mortgage so it's paid off by the time they stop working. That approach balances growth, flexibility and the security of a paid-off home. Revisit the split whenever your income, rate or goals change.

When not to pay extra

Skip extra payments if you don't have an emergency fund, if you're carrying credit card or other high-rate debt, or if you're not getting your full retirement match. Those come first.

Next, check whether a refinance makes sense, compare investing vs paying off debt and see your full mortgage payment.