What would an extra payment save you?
See the interest you'd avoid and the years you'd cut off your mortgage, calculated on your real balance.
Roughly how much longer you have to pay, not the loan’s original term.
Enter your balance and rate to see what an extra payment saves you.
Tell your servicer to apply it to principal. An extra amount sent without instructions is often credited toward next month's bill instead, which doesn't change your balance or these numbers. See how extra payments actually hit your amortization.
Paying extra shortens the loan; it doesn't reduce your required monthly payment. If a lower payment is the goal, that's a recast or refinance.
Estimates only: not financial advice. Verify with your lender. Your numbers stay in your browser.
How this works
We rebuild your real amortization schedule
Your balance, rate, and remaining years are amortized month by month, then the whole schedule is rebuilt with your extra payment applied. The difference between the two is your saving, not an approximation from a rule of thumb.
Monthly extras and lump sums both count
Add a recurring amount, a one-time payment, or both together. A lump sum today and the same amount spread over a year produce different results, and the calculator reflects that.
PMI comes off sooner, and we show it
Extra principal reaches the 80% loan-to-value cancellation threshold ahead of schedule. Add your original home value and PMI amount and the calculator prices that saving alongside the interest.
Estimates only, not financial or legal advice. Verify with your lender.
Common questions
It depends almost entirely on your rate and how much of the loan is left. On a $340,000 balance at 6.5% with 30 years to run, an extra $100 a month saves roughly $70,000 in interest and clears the loan about 4 years early. The same $100 on a loan with 8 years left saves a few thousand. Enter your own balance above rather than relying on a rule of thumb, because the gap between those two cases is enormous.
Interest is charged on the balance you still owe, so a dollar of principal paid today avoids interest on every month that follows. In the first years of a mortgage most of your payment is interest and the balance barely moves, which is precisely when an extra dollar has the most remaining months to work across. The same dollar paid in year 25 has almost no time left to save anything.
No. Extra principal shortens the loan; it does not reduce the payment your servicer requires each month. If a lower payment is what you need, the tools for that are a recast (same loan, re-amortized over the remaining term after a lump sum, typically a $150–500 fee) or a refinance (an entirely new loan, rate, and closing costs).
Yes, and this is the single most common way extra payments get wasted. An unlabelled extra amount is frequently applied to next month's bill instead of the balance, which pays you ahead in time but does nothing to your amortization or your PMI timeline. Designate it as "additional principal" in your servicer's portal or on the memo line, then check your next statement to confirm the balance dropped by the full amount.
It moves up the date you can request cancellation. Under the Homeowners Protection Act you may ask your servicer to cancel PMI once the balance reaches 80% of the original value, and extra principal legitimately gets you there sooner. The separate automatic termination at 78% is measured against your original amortization schedule, so extra payments do not move that date. Add your original home value and PMI amount above to see the difference.
Paying extra earns a guaranteed, tax-free return equal to your mortgage rate, which is a genuinely good risk-free return when rates are high. Investing may return more over long periods but carries risk and is not guaranteed. This calculator shows only the mortgage side of that comparison, and the answer also depends on your emergency savings, retirement match, and any higher-interest debt. It is not financial advice.
No. The calculation runs entirely in your browser and none of the figures you type are transmitted or stored.
Stop checking this by hand
Run your free mortgage health check once, and CasaCrow keeps watching — PMI eligibility, escrow drift, and today's rates — then tells you the day it's worth acting.