United States version
What this tool answers
Start with a balance and a proposed monthly payment. This tool solves for payoff time, including a smaller final payment when appropriate. Older saved scenarios that provide a term instead of a payment retain their scheduled-payment fallback.
Formula
For positive r, n = −ln(1 − P × r / M) / ln(1 + r); round up the payment count and adjust the final payment.
Worked example: Thirty payments to clear a balance
With $9,000 outstanding, a 0% annual rate and a $300 monthly payment, payoff takes exactly 30 months. The final payment is $300 and total interest is $0.
Load these worked-example inputs
Limitations
Rates and payments stay constant. Fees and new borrowing are excluded. A payment that does not exceed the monthly interest cannot pay off a positive-rate balance in this model.
Frequently asked questions
Why is my payment too small to produce a payoff date?
When the payment is no larger than monthly interest, principal does not decrease under this model.
Why might the last repayment be smaller?
Only the remaining balance plus that month’s interest needs to be paid in the final period.
How are older term-based repayment links handled?
When no explicit monthly payment is supplied, the original term derives the scheduled payment and any extra payment is added before payoff is simulated.