Extra Mortgage Payment Calculator
Adding even a small amount to every payment goes straight to principal, which snowballs over time. See how many years it shaves off your loan and how much interest it saves.
Interest saved
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Every extra dollar goes straight to principal, so it stops accruing interest for the rest of the loan. The earlier in the loan you start, the larger the effect.
Why a little extra goes a long way
Early in a mortgage, most of each payment goes to interest and only a sliver to principal. Any extra you add skips the interest entirely and knocks down the balance directly. Because interest is charged on the remaining balance every month, a smaller balance today means less interest charged for every month that follows — the saving compounds.
That's why an extra $300 a month on a $350,000 loan can cut roughly eight years off a 30-year mortgage and save well over $100,000 in interest. You're not just paying the loan off sooner; you're erasing all the interest that would have accrued on those years.
How the calculator works
It builds your amortization schedule month by month. Each month it charges interest on the balance, applies your normal payment plus the extra amount, and reduces the balance — repeating until the loan hits zero. It does the same with no extra payment, then compares the two:
time saved = original payoff months − new payoff months
The "base monthly payment" is your normal principal-and-interest amount; the extra is added on top of it every month.
Ways to add extra without feeling it
- Round up. Rounding a $2,212 payment to $2,400 quietly adds principal every month.
- One extra payment a year. Splitting a 13th payment across the year (paying 1/12 extra monthly) has a similar effect to biweekly payments.
- Apply windfalls. Tax refunds and bonuses sent to principal make a noticeable dent.
Before committing, weigh it against other goals: if your mortgage rate is low, investing the extra or paying off higher-interest debt first may beat prepaying. And confirm your servicer applies the extra to principal, not to next month's payment.
Frequently asked questions
Is it better to pay extra or recast?
Paying extra shortens the loan while keeping the same required payment. A recast keeps the payoff date but lowers the required payment after a lump sum. Choose based on whether you want a faster payoff or lower required payments.
Should I pay extra or invest instead?
It depends on your rate and risk tolerance. Prepaying a mortgage is a guaranteed return equal to your interest rate. If you can reliably earn more after tax by investing — or you carry higher-interest debt — that may come first.
Does it matter when in the loan I start?
Yes. The earlier you add extra principal, the more future interest you erase, so the savings are largest at the start of the loan and shrink as you near payoff.