> For the complete documentation index, see [llms.txt](https://yung-pixels.gitbook.io/whitepaper/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://yung-pixels.gitbook.io/whitepaper/technological-overview/why-is-usdlink-needed.md).

# Why is $LINK needed?

To put it short, Chainlink requires $LINK on its [**VRF**](https://docs.chain.link/docs/chainlink-vrf/).

The revealing process is powered by [**VRF**](https://docs.chain.link/docs/chainlink-vrf/), and it needs $LINK to provide the on-chain randomness. That $LINK is added to the contract subscription balance at the VRF Coordinator contract.\
\
At the revealing moment, we request a $LINK value, based on this calculation:

`((Gas price * (Verification gas + Callback gas)))/ (ETH/LINK) + Chainlink Charge = Total gas cost`

> See more about this [**calculation**](https://docs.chain.link/docs/chainlink-vrf/#subscription-billing)

The $LINK required to reveal depends on the ETH/LINK ratio, which can change over time, although it is very stable. The value of LINK is also provided by Chainlink's [**Data Feeds**](https://docs.chain.link/docs/using-chainlink-reference-contracts/), so everything used to provide relevant data and randomness exists on-chain.

The calculation is required by Chainlink to cover all the costs up to the value obtained through the equation above.