Why extra payments work
Mortgages are front-loaded with interest. In the early years, the majority of each payment covers interest rather than reducing what you owe. When you add an extra payment that goes entirely to principal, you permanently remove that amount from the balance — and all of the future interest it would have generated. That is why even modest extra payments have an outsized effect on your payoff date and total interest.
This calculator derives your standard principal-and-interest payment from your balance, rate, and term, then runs two amortization schedules side by side: one with your normal payment and one with the extra amounts applied. The difference is the time and interest you save.
Ways to make extra payments
There is no single right way to pay extra — the best method is the one you will actually stick to. Common approaches include:
- A fixed extra amount each month. Add the same dollar amount to every payment so the savings compound steadily and predictably.
- Biweekly payments. Pay half your payment every two weeks to make 13 full payments a year instead of 12, without feeling a large monthly hit.
- One-time lump sums. Direct tax refunds, bonuses, or inheritance windfalls straight at the balance. The earlier the lump sum lands, the more interest it wipes out.
- Rounding up. Round each payment up to the nearest hundred so the extra goes to principal almost painlessly.
Lump sum vs. recurring extra payment
Both a one-time lump sum and a recurring monthly extra reduce principal and save interest — they just work differently. A lump sum delivers an immediate balance reduction, so it saves the most when applied early in the loan. A recurring extra payment is smaller each month but compounds steadily over the years. The table below compares both on a $300,000 mortgage at 6.5% over 30 years.
| Approach | Years saved | Interest saved | Best for |
|---|---|---|---|
| One-time $10,000 lump sum (now) | About 3 years | About $54,000 | A windfall you have today |
| $200 extra every month | About 7 years | About $103,000 | Steady, ongoing budget room |
Estimates for illustration. The most powerful approach is usually an early lump sum plus ongoing extra payments — enter both in the calculator above to see your own numbers.
What happens if I make 2 extra payments a year?
Making two extra full payments a year — beyond your normal twelve — sends a meaningful amount straight to principal and can shorten a typical 30-year mortgage by roughly eight to ten years while saving tens of thousands in interest, depending on your rate and balance. The simplest way to do it without feeling a large hit is to split the cost across the year: set aside one-sixth of a payment each month, or pay biweekly so the calendar produces the equivalent of one extra payment annually. As always, tell your servicer to apply the extra to “principal only.”
Pros and cons of paying extra
Benefits
- Shortens your loan by years and cuts total interest.
- A guaranteed return equal to your mortgage rate.
- Flexible — pay extra only when it suits your budget.
- Builds home equity faster.
Trade-offs
- Money in equity is less liquid than cash savings.
- Your required monthly payment does not go down.
- Investing may beat a low mortgage rate over the long term.
- A few loans carry a prepayment penalty — confirm first.
Tips for making extra payments count
- Specify “principal only.” Tell your servicer to apply extra amounts to principal, or they may credit your next scheduled payment instead.
- Pay extra early in the loan. Extra principal saves the most interest in the early, interest-heavy years of the mortgage.
- Cover the essentials first. Fund an emergency reserve, capture any employer retirement match, and pay off higher-interest debt before accelerating a low-rate mortgage.