Online Tool Store
Extra Payment Calculator
Estimate how extra monthly principal payments can shorten a loan, reduce interest, and move up your payoff date in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Early payoff planner
How much faster could extra principal work?
Scheduled payment
$1,770
New payment
$2,020
Interest saved
$0
Time saved
0 months
Payoff comparison
Payoff date estimate
Sooner
This is a fixed-rate estimate for principal and interest only. Confirm prepayment rules and exact payoff figures with your lender.
How it works
- Enter the current balance, APR, and years remaining on the loan.
- Add the extra amount you plan to pay toward principal each month.
- Compare the regular payoff schedule with the faster schedule, including interest and time saved.
The payoff math
monthly payment = P x r / (1 - (1 + r)^(-n))
Each month, interest is calculated on the remaining balance first. The regular payment plus any extra principal reduces that balance, and the schedule repeats until the loan reaches zero.
FAQ
What counts as an extra payment?
An extra payment is any amount applied directly to principal on top of the required monthly payment. It reduces the balance sooner, so less interest accrues later.
Does this include taxes and insurance?
No. The estimate focuses on fixed-rate principal and interest. Escrow items, fees, PMI, and lender-specific rules are not included.
Can this be used for car or personal loans?
Yes, if the loan uses fixed monthly amortization and allows principal prepayments. Use the current balance, APR, remaining term, and planned extra amount.
What if my lender has prepayment penalties?
This interface does not model penalties. Check your loan terms before making extra payments, especially on mortgages or business loans.
Is my loan information uploaded?
No. The payoff estimate runs entirely in your browser and does not send your numbers anywhere.
How we compare
| Feature | Online Tool Store | Mortgage servicer portal | Spreadsheet model |
|---|---|---|---|
| Time and interest saved | Automatic | Sometimes | Formula required |
| Works while editing inputs | Yes | Usually no | Depends |
| Prepayment penalty modeling | No | Loan-specific | Custom |
| Runs privately in-browser | Yes | No | Local file |
Use this calculator for quick payoff planning, then confirm exact principal-only payment handling and any penalties with your lender.