Reverse loan rate
Infer nominal annual and monthly rates from principal, fixed payment and term using a stable bisection solver.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Reverse-loan JSON
Rate result
Nominal APR is inferred under equal-installment repayment.
Enter reverse-loan JSON to calculate
: 0 · : 0
What this tool does
- Verify the rate implied by a quoted monthly payment.
- Estimate nominal APR from an actual payment.
Example
Input
{"principal":100000,"payment":2987.09,"months":36}Output
Annual rate / 年利率: 4.78% Monthly rate / 月利率: 0.40%
Principal and payment are currency amounts; rates are percentages under a non-negative equal-installment model.
Frequently asked questions
Why can payment not be too low?
It must be at least principal divided by term; otherwise no non-negative-rate solution exists.
Is the solution approximate?
A 100-iteration bisection gives a sufficiently precise floating-point result.
Is the output effective APR?
No. It is nominal APR, with monthly rate equal to APR divided by 12.
Keywords：反算利率贷款利率名义年利率loan rateAPRbisection