Extra Mortgage Payment Calculator
Adding even $100 to a mortgage payment attacks principal directly. Enter an extra amount to see exactly how many months you cut from the loan and how much interest never gets charged.
Your results
Charts & visualization
Balance: standard vs accelerated payoff
The gap between the curves is equity created ahead of schedule.
Every chart’s underlying numbers are available as text — use the “view as table” control under each chart.
How it works
The tool computes two complete amortization schedules from the same loan: one at the required payment, one at that payment plus your extra amount. The math is identical — the only difference is that every extra dollar reduces principal immediately, so every later month charges interest on a smaller balance.
The summary reports months removed from the schedule and lifetime interest avoided. Economically, avoiding 6.5% mortgage interest behaves like earning a guaranteed 6.5% return on that money — useful when comparing against investing the same cash.
Formula used
Payment— standard scheduled paymentExtra— additional principal contributed each monthSavings— baseline total interest − accelerated total interest
Example calculation
On a $304,000 loan at 6.5%, an extra $200 per month retires the debt in about 23.2 years instead of 30 years — cutting roughly 6 yrs 10 mo from the schedule — and saves about $103,860 in interest. Those extra payments behave like a guaranteed, tax-free return equal to the mortgage rate.
Assumptions & limitations
- Extras are applied monthly, immediately after the regular payment.
- No prepayment penalty assumed; verify your loan terms.
- Compares interest within the loan only; it does not model investing the extra cash elsewhere.
- Escrow items (tax, insurance) are unaffected and excluded.
Results are planning estimates based on your inputs and the stated assumptions — not financial advice or a loan offer. Verify important figures with your lender or advisor.
Frequently asked questions
Is it better to pay extra on my mortgage or invest?
Paying extra earns a guaranteed return equal to your mortgage rate; investing offers higher expected returns with real risk. A common order of operations: capture any employer 401(k) match first, keep an emergency fund, then decide based on your rate and risk tolerance.
Should I pay extra monthly or once a year?
Monthly extras win slightly because principal drops earlier. A lump annual sum still helps meaningfully — consistency matters more than timing.
How do I make sure extras go to principal?
Mark the payment “apply to principal” with your servicer and confirm on the next statement. Unmarked amounts are sometimes parked in escrow or applied to next month’s bill, which saves nothing.
Does a biweekly plan accomplish the same thing?
Biweekly plans create one extra full payment per year — similar to a modest monthly extra. You can replicate it free by dividing that amount by 12 and adding it to each monthly check.