# Reserve Factor

The reserve factor defines the portion of borrower interest that is converted into [reserves](https://docs.belugas.io/atokens/total-reserves).

**BErc20 / CEther**

```
function reserveFactorMantissa() returns (uint)
```

* `RETURN`: The current reserve factor as an unsigned integer, scaled by 1e18.

**Solidity**

```
BErc20 bToken = BToken(0x3FDA...);
uint reserveFactorMantissa = bToken.reserveFactorMantissa();
```

**Web3 1.0**

```javascript
const bToken = CEther.at(0x3FDB...);
const reserveFactor = (await bToken.methods.reserveFactorMantissa().call()) / 1e18;
```