> For the complete documentation index, see [llms.txt](https://docs.agilefi.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.agilefi.org/getting-started/protocol-math/calculating-the-apy-using-rate-per-block.md).

# Calculating the APY Using Rate Per Block

The Annual Percentage Yield (APY) for supplying or borrowing in each market can be calculated using the value of `supplyRatePerBlock` (for supply APY) or `borrowRatePerBlock` (for borrow APY) in this formula:

```
Rate = aToken.supplyRatePerBlock(); // Integer
Rate = 37893566
ETH Mantissa = 1 * 10 ^ 18 (ETH has 18 decimal places)
Blocks Per Day = 4 * 60 * 24 (based on 4 blocks occurring every minute)
Days Per Year = 365

APY = ((((Rate / ETH Mantissa * Blocks Per Day + 1) ^ Days Per Year - 1)) - 1) * 100
```

Here is an example of calculating the supply and borrow APY with Web3.js JavaScript:

```javascript
const ethMantissa = 1e18;
const blocksPerDay = 4 * 60 * 24;
const daysPerYear = 365;

const aToken = new web3.eth.Contract(sEthAbi, sEthAddress);
const supplyRatePerBlock = await aToken.methods.supplyRatePerBlock().call();
const borrowRatePerBlock = await aToken.methods.borrowRatePerBlock().call();
const supplyApy = (((Math.pow((supplyRatePerBlock / ethMantissa * blocksPerDay) + 1, daysPerYear))) - 1) * 100;
const borrowApy = (((Math.pow((borrowRatePerBlock / ethMantissa * blocksPerDay) + 1, daysPerYear))) - 1) * 100;
console.log(`Supply APY for ETH ${supplyApy} %`);
console.log(`Borrow APY for ETH ${borrowApy} %`);
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.agilefi.org/getting-started/protocol-math/calculating-the-apy-using-rate-per-block.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.