Mortgage Extra Payment Calculator
New payoff time, interest saved, and total paid from balance, rate, term, and extra.
What it does
Extra principal shortens a mortgage from both ends: each added dollar skips its own future interest, and the freed interest pays the next principal sooner. A modest monthly extra compounds into years shaved and five figures saved.
The tool above takes balance, rate, term, and monthly extra. It returns the new payoff time with interest saved and total paid beside them.
The default of $300,000 at 6.5% over 30 years with $200 extra pays off in 23 yr 1 mo instead of 30 yr 0 mo, saving $103,448.79 of interest for $579,184.67 total. With zero extra the same loan costs $682,633.47.
The mechanics follow federal home loan guidance with mortgage servicing rules matching each term. Both treat extra as principal prepayment and warn that prepayment penalties, where they exist, are agreed at closing.
How to use
- Enter the current loan balance owed.
- Enter the annual rate and original term.
- Enter the monthly extra toward principal.
- Read the new payoff time first.
- Read interest saved to price the habit.
Formula
- base
- Scheduled amortizing payment at the contract rate.
- extra
- Added principal each month on top of base.
- saved
- Base total minus accelerated total.
The final month pays the leftover plus its interest, slightly less than a full payment. Biweekly plans equal about one extra monthly payment a year; confirm no program fees first.
Worked example
Example: $300,000 at 6.5%, $200 extra
Defaults: balance 300000, rate 6.5%, 30 years, extra 200.
- Base payment amortizes to $682,633.47 over 360 months.
- Extra $200 joins principal every month from month one.
- Simulation clears the balance in month 277: 23 yr 1 mo.
- Total paid drops to $579,184.67.
- Tool shows 23 yr 1 mo (was 30 yr 0 mo), $103,448.79 saved, $579,184.67 total.
Reference table
| Extra/mo | Payoff | Interest saved |
|---|---|---|
| $0 | 30 yr 0 mo | $0.00 |
| $100 | 26 yr 0 mo | $60,994.79 |
| $200 | 23 yr 1 mo | $103,448.79 |
Limits
- Principal and interest only; taxes and insurance ride along.
- Fixed rate assumed; ARMs reset the math.
- Prepayment penalties, where agreed, sit outside.
- Extra must be applied to principal by the servicer.
Common mistakes
- Paying extra without confirming principal application.
- Buying biweekly programs that free extra payments match.
- Raiding emergency funds to chase interest savings.
- Ignoring higher rate debts that cost more.
- Stopping extra after rates fall instead of refinancing.
Try it yourself
Quick checks. Answers sit tucked under each question.
$200,000 at 7% over 30 years with $100 extra?
Pays in 24 yr 3 mo, saving $63,308.63 ($415,709.16 total).
Zero extra?
No change: 30 yr 0 mo, $0.00 saved, $682,633.47 total.
Biweekly instead?
26 half payments equal 13 monthly: about one extra payment a year, same effect free.
Questions
How much does $200 extra save?
On the example: 6 yr 11 mo sooner and $103,448.79 less interest.
Where does extra go?
Tell the servicer: principal. Otherwise it may sit as future payments.
Any penalty for prepaying?
Only if agreed at closing. Most modern loans carry none; check the note.
Extra or refinance?
Extra keeps flexibility; refinancing cuts the rate for a fee. Compare both totals.
Extra or invest?
Extra earns the mortgage rate risk free; investing may beat it with risk attached.
Does extra remove PMI early?
Often yes: faster principal can reach 80% LTV sooner for PMI cancellation review.
Sources
- CFPB: Your home loan toolkit (prepayment advantages, PDF)
- CFPB: Mortgage servicer extra principal payments (PDF)