> For the complete documentation index, see [llms.txt](https://payc-finance.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://payc-finance.gitbook.io/docs/what-is-apy.md).
# What is APY?
**APY** stands for Annual Percentage Yield. This measures the real rate of return on your principal tokens amount by taking into account the effect of compounding interest. In the case of PAYC Finance Protocol, your $PAYC Finance tokens represent your principal, and the compound interest is added periodically on every Rebase event (Every 15 minutes).
Your new principal amount is your then current Mind token amount, plus your new rebase token amount. This total amount is what gets calculated for your next rebase rewards.
One interesting fact about APY is that your balance will grow not linearly but exponentially over time! Assuming a 15 minute compound interest of **0.02355%**, if you start with a balance of 1 $PAYC Finance on day 1, after a year, your balance will grow to **3,831.25** **$PAYC Finance**. That is the power of compound interest! Use the formula below:
