# ERC-20 Paymaster Architecture

:::info
You can view the whole ERC-20 Paymaster contract [in our repository](https://github.com/pimlicolabs).

This paymaster is an onchain contract, we can not guarantee that using the paymaster is risk-free. Please use the paymaster at your own risk.
:::

## Design

Pimlico's ERC-20 Paymaster is an ERC-4337 Paymaster that relies on an offchain API, powered by Pimlico, to supply the user with an up-to-date token price, alongside a signature from a valid signer address. The paymaster is able to pay for the gas fees of your users in exchange for ERC-20 tokens that are drawn from the user.

## Estimating the amount of tokens required for a user operation

After calling the `pimlico_getTokenQuotes` function, the Pimlico API will return two important values, `exchangeRate` and `postOpGas`. You can use these two values, alongside information about the user operation you're looking to sponsor, to get an estimate of the amount of tokens required for the user operation.

You can do this by using [this onchain function](https://github.com/pimlicolabs) on the paymaster.