Definition
APY is the effective annual rate after compounding. It makes products with different compounding frequencies easier to compare.
Formula
APY = (1 + APR/n)^n - 1
Example
If APR is 12% and compounding is monthly (n=12), APY = (1+0.12/12)^12 - 1 = 12.68%.
How to use it
- APY includes compounding; APR does not.
- The difference between APR and APY grows with more frequent compounding.
- Use APY for savings yields and APR for loan costs.
- Compare products with the same compounding frequency when possible.
- Ask whether the rate is fixed or variable; APY can change with rate resets.
Common mistakes
- Comparing APY on one product to APR on another.
- Ignoring fees that reduce the effective yield.
- Mixing nominal APR assumptions with effective APY outcomes.
- Using a teaser APY without checking how long it lasts.
Measured as
APY = (1 + APR/n)^n - 1
Misused when
- Comparing APY on one product to APR on another.
- Ignoring fees that reduce the effective yield.
- Mixing nominal APR assumptions with effective APY outcomes.
- Using a teaser APY without checking how long it lasts.
Operator takeaway
- APY includes compounding; APR does not.
- The difference between APR and APY grows with more frequent compounding.
- Use APY for savings yields and APR for loan costs.
- Tie APY (Annual Percentage Yield) to the same balance-sheet date, scenario, and decision memo you are using elsewhere in the model.
- Document which claims, costs, or adjustments your team includes before comparing numbers across forecasts, covenants, or valuation work.
Next decision
- Quantify the impact with APR to APY Calculator if you need to turn the definition into an operating assumption.
- Read APR vs APY: how compounding changes the effective rate if the decision depends on interpretation, policy, or trade-offs beyond the raw formula.
Where to use this on MetricKit
Calculators
- APR to APY Calculator: Convert APR to APY (and APY to APR) given compounding frequency.
Guides
- APR vs APY: how compounding changes the effective rate: A practical guide to APR vs APY: what each means, how to convert between them, and common comparison mistakes.
- Capital budgeting hub: NPV, IRR, payback, and investment decisions: A practical hub for capital budgeting: use NPV, IRR, discounted payback, and profitability index together (and avoid relying on a single metric).