Back out the interest rate implied by a loan payment.
How to use this calculator
Every field updates the result as you type — there is no submit step. The inputs below are pre-filled with a realistic example so you can see how the tool behaves before entering your own figures.
| Field | Unit | What it means |
|---|---|---|
| Loan amount | $ | Enter a numeric value. |
| Payment | $ | Enter a numeric value. |
| Number of payments | — | Enter a numeric value. |
| Payments per year | — | Choose one of the available options. |
Worked example
Using the default values loaded into the calculator above, the result is:
| Input | Value |
|---|---|
| Loan amount ($) | 20000 |
| Payment ($) | 400 |
| Number of payments | 60 |
| Payments per year | Monthly |
| Output | Value |
|---|---|
| Nominal annual rate | 7.4201% |
| Rate per period | 0.618341% |
| Effective annual rate | 7.6777% |
| Total interest | $4,000.00 |
Reading the result
Financial projections compound small assumption changes into large differences over time. Rates, fees and tax treatment vary by lender and jurisdiction, so treat the output as a well-structured estimate for comparing options rather than a quotation.
Figures that change annually — tax bands, contribution limits, statutory rates — are exposed as editable inputs. Check them against current published values before relying on the result.
Sharing and saving a calculation
The "Copy link" button encodes every value you have entered into the page URL. Opening that link restores the calculation exactly, which makes it easy to bookmark a scenario, send it to someone else, or keep several variations side by side in separate tabs.
Frequently asked questions
What does the Interest Rate Calculator do?
Back out the interest rate implied by a loan payment.
What result do the default values produce?
With the values pre-loaded in the calculator, nominal annual rate comes to 7.4201%.
Is this calculator free to use?
Yes. It is free, requires no account, and runs entirely in your browser — nothing you enter is transmitted or stored on a server.
Can I save or share a calculation?
Yes. The "Copy link" button builds a URL containing all your entered values. Anyone opening that link sees the same calculation.
How accurate is the result?
The calculation itself is exact for the inputs given. Real-world accuracy depends on how well those inputs reflect your actual situation, so review the assumptions before relying on the figure.