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Calculators / Finance / Mortgage extra payment
Mortgage extra payment calculator
Estimate how an extra monthly payment changes a fixed-rate mortgage payoff.
On this page
Months with scheduled payment207.89months
Months with extra payment176.94months
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How to calculate
Estimate how an extra monthly payment changes a fixed-rate mortgage payoff.
Months with scheduled payment = -ln(1-balance*(apr/1200)/payment)/ln(1+apr/1200); Months with extra payment = -ln(1-balance*(apr/1200)/(payment+extra))/ln(1+apr/1200)
Worked example
Current balance: 250000; Scheduled monthly payment: 1800; Extra monthly payment: 200; Annual interest (%): 5.
Months with scheduled payment: 207.89 months; Months with extra payment: 176.94 months.
Assumptions and limits
Payments must exceed monthly interest. The logarithmic model assumes a constant rate, monthly compounding and no fees or escrow.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Estimate how an extra monthly payment changes a fixed-rate mortgage payoff. The displayed figures use the inputs and formula shown on this page.
When this tool is useful
Use the mortgage extra payment to compare a scenario, check an estimate, or verify a manual calculation.
Understanding your inputs
| Input | What to enter |
|---|---|
| Current balance | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Scheduled monthly payment | Enter a number of at least 0.000001 and no more than 1000000000000. |
| Extra monthly payment | Enter a number of at least 0 and no more than 1000000000000. |
| Annual interest (%) | Enter a number of at least 0.000001 and no more than 100. |
Frequently asked questions
What should I check before using the mortgage extra payment result?
Payments must exceed monthly interest. The logarithmic model assumes a constant rate, monthly compounding and no fees or escrow.
Is this mortgage extra payment result exact?
It is exact for the stated mathematical model and entered values. Real-world results can differ when rates, timing, fees, definitions or measurement conditions differ.