Finance & Money
APY Calculator
Convert a nominal annual rate to its periodic rate and effective annual percentage yield, then project an opening balance across the entered number of years. Results separate starting capital from modeled compound growth.
Periodic rate-
Effective annual yield-
Projected ending balance-
Projected growth-
Exact scenario comparison
Nominal annual rate (%) scenarios
Exact scenario comparisonNominal annual rate (%) changes while all other entered assumptions remain constant.
| Nominal annual rate (%) | Periodic rate | Effective annual yield | Projected ending balance | Projected growth |
|---|
Period-by-period detail
Monthly schedule and annual summary
How to use APY Calculator
- Enter the nominal annual rate, number of compounding periods per year, opening balance, and projection years.
- Review the periodic rate and effective APY before comparing projected ending balance and modeled growth.
- Match the frequency and rate basis to the product disclosure and account separately for deposits, withdrawals, taxes, and changing rates.
Calculator guide
Understanding APY Calculator
A nominal deposit rate does not show the full effect of compounding. APY converts the entered nominal rate and compounding frequency into one effective annual yield, then applies that yield to a multi-year balance projection without mixing in deposits or withdrawals.
Calculation method
How the calculation works
Convert the nominal rate to a periodic rate, compound it for one year to obtain APY, and apply that effective yield across the projection. Convert the nominal rate to a periodic rate, compound it for one year to obtain APY, and apply that effective yield across the projection.
Worked situations
Practical examples
- A 5% nominal rate compounded monthly has a periodic rate of 5% divided by 12 and an APY slightly above 5%.
- Compare accounts using the same opening balance and years while entering each product's stated nominal rate and compounding frequency.
- If the institution already quotes APY, do not enter that APY as the nominal rate unless compounding is set consistently for that purpose.
Better inputs
Useful tips
- Confirm whether interest compounds daily, monthly, quarterly, or on another schedule.
- Compare minimum balances, rate tiers, promotional periods, withdrawal restrictions, and fees in addition to APY.
- Use an after-tax or inflation-adjusted tool when purchasing power rather than account balance is the decision metric.
Before relying on the result
Limitations and common mistakes
- The model assumes a constant nominal rate and regular compounding for the entire horizon.
- Deposits, withdrawals, taxes, fees, rate tiers, promotional expirations, day-count conventions, and early-withdrawal penalties are excluded.
- Projected growth is mathematical compounding, not a guarantee from a bank, issuer, or investment product.
Reference
Key terms
- Nominal annual rate
- Stated annual rate before reflecting within-year compounding.
- Periodic rate
- Nominal annual rate divided by the number of compounding periods per year.
- APY
- Effective percentage growth over one year after within-year compounding.
- Compound growth
- Interest earned on the opening balance and on previously credited interest.
Important note
Calculated from the entered values and stated financial terms. It is not a product quote, lending decision, tax filing, or investment recommendation.
Frequently asked questions
Why is APY higher than the nominal rate?
Positive interest credited during the year earns additional interest in later compounding periods.
Does more frequent compounding always matter greatly?
It increases APY for the same positive nominal rate, but the incremental difference becomes smaller as frequency rises.
Can APY compare a loan and a savings account?
APY is a deposit-yield convention. Borrowing comparisons normally use APR and the actual payment schedule.
Does the balance projection include recurring deposits?
No. It compounds one opening balance only; use a savings projection with contribution timing when deposits recur.