Exchange Rate

Each fToken is convertible into an ever increasing quantity of the underlying asset, as interest accrues in the market. The exchange rate between an fToken and the underlying asset is equal to;

exchangeRate = (getCash() + totalBorrows() - totalReserves()) / totalSupply()

FBep20 / FBnb

function exchangeRateCurrent() returns (uint)

• RETURN: The current exchange rate as an unsigned integer, scaled by 1e18

Solidity

FBep20 fToken = FToken(0x3FDA...);
uint exchangeRateMantissa = fToken.exchangeRateCurrent();

Web3 1.0

const fToken = FBnb.at(0x3FDB...);
const exchangeRate = (await fToken.methods.exchangeRateCurrent().call()) / 1e18;

Tip: note the use of call vs. send to invoke the function from off-chain without incurring gas costs.