If a lender only tells you the payment, this works out the rate you are really paying. Including upfront fees gives the APR, which is the fair way to compare loan offers.
How to use the Interest Rate Calculator
- Calculate for
- Loan amount
- Periodic payment
- Term
- Payment frequency
- Upfront fees
- Initial deposit
- Current balance
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose loan or deposit and enter the figures.
Tips
- Use the nominal annual rate and pick the compounding frequency your bank or broker states.
- Small differences in return or fees compound into large differences over decades.
- Run the calculation with a cautious, a central and an optimistic return to see the range of outcomes.
- Past returns do not guarantee future returns – nothing here is investment advice.
Common mistakes to avoid
- Comparing an APR with an APY or effective rate.
- Ignoring inflation, taxes and fees when judging a real return.
- Entering a percentage as a decimal (5 instead of 0.05 is correct here).
Inputs explained
| Field | What to enter |
|---|---|
| Calculate for | Choose one: Loan, Deposit |
| Loan amount | Amount in your currency |
| Periodic payment | Amount in your currency |
| Term | Units: years, months |
| Payment frequency | Choose one: Monthly, Semi-monthly, Bi-weekly, Weekly … |
| Upfront fees | Amount in your currency |
| Initial deposit | Amount in your currency |
| Current balance | Amount in your currency |
What each result means
- Annual interest rate (nominal) = [Periodic rate]×[Payment frequency]
- Effective annual rate = ((1 + [Periodic rate]÷100)^[Payment frequency] – 1)×100
Example values
How the main result changes when Loan amount changes and everything else stays at the example values above:
| Loan amount | Annual interest rate (nominal) (%) |
|---|---|
| 10,000 | 41.868 |
| 15,000 | 20.31 |
| 20,000 | 7.42 |
| 25,000 | -1.595 |
| 30,000 | -8.455 |
| 40,000 | -18.534 |
Formula
Loan: solve P = PMT × [1 − (1 + i)^−n] ÷ i for i; nominal rate = i × payments per yearDeposit: rate = (balance ÷ deposit)^(1 ÷ years) − 1APR: same calculation using loan amount minus feesWorked example
Inputs — Calculate for: Loan; Loan amount: $20,000; Periodic payment: $400; Term: 5 years; Payment frequency: Monthly; Upfront fees: $300; Initial deposit: $10,000; Current balance: $11,500.
Results — Periodic rate = 0.6183 %; Annual interest rate (nominal) = 7.42 %; Effective annual rate = 7.678 %; APR (including fees) = 8.059 %; Total interest = $4,000.00.
Frequently asked questions
How do I find the interest rate on a loan?
Solve the loan payment formula for the rate – this calculator does it numerically.
What is the difference between the interest rate and APR?
APR includes fees, so it is higher when fees are charged.
Why does the effective rate exceed the nominal rate?
Because interest compounds within the year.
What formula does the Interest Rate Calculator use?
Loan: solve P = PMT × [1 − (1 + i)^−n] ÷ i for i; nominal rate = i × payments per year.