Extra Payment Calculator
Test whether sending extra money each month meaningfully shortens payoff time before you commit to it.
Calculator
Extra Payment Calculator
Enter the loan balance you want to pay down faster.
Use the annual rate on the loan.
Enter the amount you normally pay each month.
Add the recurring extra amount you may pay each month.
Example values are loaded.
Result
Your result
Adding $250.00 per month would shorten payoff by about 8 years 3 months and save roughly $108,124.41 in interest.
Time saved
8 years 3 months
Interest saved
$108,124.41
New payoff time
21 years 7 months
Plan comparison
Next steps
Compare before you move on
Most people use one calculator to answer the first question and a related tool to pressure-test the decision.
Debt
Debt Payoff Calculator
Estimate how long it could take to eliminate a balance based on your interest rate and monthly payment.
Debt
Credit Card Payoff Target Calculator
Calculate the monthly payment needed to clear credit card balance by a target date, with total interest and total paid.
Borrowing
Loan Calculator
Estimate monthly loan payments, total interest, and total repayment with a standard amortized loan formula.
What this calculator shows
Extra payments feel small in the moment, but on a large balance they can remove months or years of interest because principal falls earlier.
This calculator compares the current payoff path with an accelerated plan so you can see whether the extra payment is worth the squeeze in your monthly budget.
How to use it
- 1. Enter the current balance and interest rate on the loan.
- 2. Add the regular monthly payment you already make.
- 3. Test an extra monthly payment to compare time saved and interest saved.
Formula and assumptions
The payoff path is simulated month by month by applying interest to the remaining balance and then subtracting the payment amount.
The comparison uses the same balance and rate for both the regular plan and the accelerated plan with the extra monthly payment.
How to read this result
The most important output is usually the trade between time saved and interest saved. A small extra payment can look modest monthly but still remove a large amount of interest over a long payoff path.
Use the comparison to decide whether the extra payment should become a standing part of the plan or stay flexible. The math is strongest when the overpayment is repeatable, not aspirational.
If the savings look weaker than expected, the next question is whether the balance, rate, or regular payment is the real issue. In some cases refinancing or a different payoff target changes the picture more than a small overpayment.
Common mistakes
Assuming every lender applies the extra payment directly to principal without checking the actual payment instructions.
Treating the maximum possible overpayment as the default plan even when it leaves no room for reserves or other debt priorities.
Looking only at months saved without checking whether the same extra cash would solve a higher-interest balance more effectively somewhere else.
Limits of this estimate
This model assumes a fixed annual rate, a fixed required monthly payment, and a recurring extra payment that is applied directly to principal.
It does not model lender-specific prepayment rules, escrow changes, adjustable rates, skipped payments, new charges, late fees, or prepayment penalties.
Use it to compare payoff pressure before you choose a payment strategy; confirm principal-only handling with the lender or servicer before acting on the estimate.
Notes
This assumes the lender applies the extra payment directly to principal and that the rate stays fixed.
Source notes
Payoff simulation
The calculator applies monthly interest to the remaining balance, subtracts the regular payment, and repeats the process for the accelerated payment scenario.
Interest savings comparison
Estimated interest saved is the difference between total interest under the regular payoff path and total interest under the extra-payment path.
Principal-only assumption
The extra-payment scenario assumes the extra amount reduces principal immediately instead of being held for future payments or applied to fees.
Worked example
An extra few hundred dollars per month on a large balance can cut years off the payoff window depending on the rate.
This example uses the default sample inputs loaded on reset. It does not update with the live calculator entries above.
Time saved
8 years 3 months
Interest saved
$108,124.41
New payoff time
21 years 7 months
Feedback
Found a problem on this page?
Report confusing fields, broken math, or missing assumptions with the exact inputs you used so the issue can be reproduced.
FAQ
FAQ
Does every lender apply extra payments to principal the same way?
No. Some loans require a specific instruction or separate principal-only payment, so confirm the lender's process before relying on the estimate.
FAQ
Why can a small extra payment save so much interest?
Because reducing principal earlier lowers the balance on which future interest is calculated, which compounds the benefit over time.
FAQ
Is it better to use a payoff target calculator or an extra payment calculator?
Use an extra payment calculator when you know what cash you can add each month. Use a payoff target calculator when you care more about a finish date and need to see the required payment to hit it.
FAQ
What should I compare next if the interest savings look small?
Usually compare refinancing, a larger regular payment, or directing the extra money toward a higher-rate balance first. The better next step depends on which debt is actually costing the most.