If you know where you started and where you ended, the compound interest rate tells you the yearly rate you effectively earned. Quoting it as a nominal rate with the bank’s compounding makes it comparable to a savings account.
How to use the Compound Interest Rate Calculator
- Initial balance
- Final balance
- Term
- Compounding frequency
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the initial and final balances, the term and the compounding frequency.
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 |
|---|---|
| Initial balance | Amount in your currency |
| Final balance | Amount in your currency |
| Term | Units: years, months |
| Compounding frequency | Choose one: Yearly, Semi-annually, Quarterly, Monthly … |
What each result means
- Effective annual rate = (([Final balance]÷[Initial balance])^(1÷[Term]) – 1)×100
- Compound interest rate (nominal) = nomr([Effective annual rate]÷100, [Compounding frequency])×100
- Interest (surplus) = [Final balance] – [Initial balance]
Example values
How the main result changes when Initial balance changes and everything else stays at the example values above:
| Initial balance | Compound interest rate (nominal) (%) |
|---|---|
| 5,000 | 17.877 |
| 7,500 | 11.038 |
| 10,000 | 6.209 |
| 12,500 | 2.476 |
| 15,000 | -0.565 |
| 20,000 | -5.348 |
Formula
Effective annual rate = (final ÷ initial)^(1 ÷ years) − 1Nominal rate for n compounding periods = n × [(1 + EAR)^(1/n) − 1]; continuous: ln(1 + EAR)Worked example
Inputs — Initial balance: $10,000; Final balance: $14,500; Term: 6 years; Compounding frequency: Monthly.
Results — Effective annual rate = 6.388 %; Compound interest rate (nominal) = 6.209 %; Interest (surplus) = $4,500.00.
Frequently asked questions
How do I find the interest rate from two balances?
Divide final by initial, take the 1/years root and subtract 1 for the effective rate.
What is the nominal rate?
The quoted yearly rate before compounding.
Why does the nominal rate depend on compounding?
More frequent compounding needs a lower nominal rate for the same growth.
What formula does the Compound Interest Rate Calculator use?
Effective annual rate = (final ÷ initial)^(1 ÷ years) − 1.