Formula and calculation method
Solve P × i / [1 − (1+i)^(−n)] = payment numerically for the monthly rate i.
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
How to use interest rate calculator
- Set Principal / amount. The example below uses 100000.
- Set Payment per month. The example below uses 1110.21.
- Set Term (years). The example below uses 10.
- Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.
Worked example
Example inputs
- Principal / amount
- 100000
- Payment per month
- 1110.21
- Term (years)
- 10
- Nominal annual interest rate (%)
- 6.00009918
- Effective annual rate (%)
- 6.16788596
Factors affecting your result
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
Changing principal / amount changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.
Frequently asked questions
How does the interest rate calculator work?
Solve P × i / [1 − (1+i)^(−n)] = payment numerically for the monthly rate i.
What inputs does Interest Rate Calculator need?
Enter principal / amount, payment per month, term (years). Choose values that correspond to the same situation and measurement convention.
How should I interpret the interest rate calculator result?
Use consistent units for all comparable inputs. The displayed result is rounded; arithmetic is performed with the full available numeric precision. Check your source measurements before relying on the result.
Are my interest rate calculator inputs uploaded?
No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.
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