Formula
APY = (1 + nominal annual rate ÷ compounding periods per year) ^ compounding periods per year − 1. Ending balance = starting balance × (1 + nominal rate ÷ n) ^ (n × years). Interest earned = ending balance − starting balance.
CalculationTime
To calculate time is to make the future less invisible.
Worked example
For a 4.75% stated annual rate compounded monthly, APY = (1 + 0.0475 ÷ 12)^12 − 1 = 4.8551%. A 10,000 starting balance held for one year grows to about 10,485.51 before fees, taxes, deposits or withdrawals.
Professional note
Master’s Tip: compare APY with APY, not stated rate with APY. If one account advertises a nominal rate and another advertises APY, convert them to the same basis before choosing.
Regional and unit assumptions
Standard or basis: general compound-interest APY arithmetic. This page is an educational and planning calculator, not financial, banking, tax, investment or product-disclosure advice.
Assumptions and limitations
- The nominal rate is entered as an annual percentage before compounding.
- Compounding periods are treated as evenly spaced and the rate is assumed constant for the selected time.
- The calculator does not include deposits, withdrawals, account fees, taxes, promotional-rate expiry, minimum balances or early withdrawal penalties.
- A comparison APY is shown for planning only; use the official product disclosure or bank terms for decisions.
- Negative rates are allowed for mathematical completeness, but real accounts may have floor, fee or disclosure rules.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
APY = (1 + nominal annual rate ÷ compounding periods per year) ^ compounding periods per year − 1. Ending balance = starting balance × (1 + nominal rate ÷ n) ^ (n × years). Interest earned = ending balance − starting balance.
Standard or basis
Standard or basis: general compound-interest APY arithmetic. This page is an educational and planning calculator, not financial, banking, tax, investment or product-disclosure advice.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master's Tip
Master’s Tip: compare APY with APY, not stated rate with APY. If one account advertises a nominal rate and another advertises APY, convert them to the same basis before choosing.
Related calculators
Questions
What does APY mean?
APY means annual percentage yield. It is the effective one-year return after interest compounding is included.
How do I calculate APY?
Divide the stated annual rate by the number of compounding periods, add 1, raise that to the number of compounding periods, then subtract 1.
Is APY higher than the stated interest rate?
Usually yes when the rate is positive and compounds more than once per year. More frequent compounding makes APY slightly higher than the nominal stated rate.
Does this APY calculator include taxes or fees?
No. It shows gross compound-interest arithmetic before taxes, account fees, minimum-balance rules, deposits, withdrawals or promotional-rate changes.
What should I print for an APY comparison?
Print the starting balance, stated rate, compounding frequency, APY, ending balance, interest earned, comparison APY, formula, date, page URL and notes area.
Calculation note
APY exists because a stated annual rate does not tell the whole story when interest compounds during the year. A clear comparison names the compounding frequency, shows the effective annual yield and keeps fees or taxes outside the pure formula.
Compounding changes the annual result
When interest is credited more than once per year, each later period can earn interest on earlier interest. APY expresses that compounded result as one annual percentage.
APY helps compare different account structures
Two accounts can quote similar rates but compound at different frequencies. Converting both to APY makes the comparison more consistent before fees, limits and account rules are considered.
The printed record should keep disclosures separate
The mathematical yield is only one part of a real banking decision. Fees, tax treatment, promotional windows, balance requirements and withdrawal rules belong in the notes or official product disclosure.