> ## Documentation Index
> Fetch the complete documentation index at: https://docs.optimism.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Fee parameters

> Reference for the fee-related SystemConfig parameters on an OP Stack chain — what each parameter controls, its setter and getter, and the OP Mainnet values.

This page catalogues the fee-related parameters a chain operator can set on the `SystemConfig` contract, from the Jovian hardfork onward.
For how fees are calculated and charged, see [transaction fees on OP Mainnet](https://docs.optimism.io/op-stack/transactions/fees#transaction-fees-on-op-mainnet).
For when and how to adjust these parameters, see the [fee tuning guide](/chain-operators/guides/management/transaction-fees-101).

<Info>
  Only the [SystemConfig owner](/op-stack/protocol/privileged-roles) can call the setter methods listed below.
</Info>

## Fee formulas

On an OP Stack chain a transaction's **Total Fee** is made of three main components:

`Total Fee = L2 Fee + L1 Fee + Operator Fee`

| Component    | Formula                                                     |
| ------------ | ----------------------------------------------------------- |
| L2 fee       | `gasUsed * (baseFee + priorityFee)`                         |
| L1 fee       | `estimatedSizeScaled * l1FeeScaled / 1e12` (see below)      |
| Operator fee | `(gasUsed * operatorFeeScalar * 100) + operatorFeeConstant` |

The L1 fee charges for posting L2 data to L1, based on the transaction's estimated compressed (FastLZ) size:

```ts theme={null}
l1FeeScaled =
  baseFeeScalar * 16 * l1BaseFee +
  blobBaseFeeScalar * l1BlobBaseFee

estimatedSizeScaled =
  max(
    minTransactionSize * 1e6,
    intercept + fastlzCoef * fastlzSize
  )

l1Fee = estimatedSizeScaled * l1FeeScaled / 1e12
```

<Info>
  **Pre-Jovian (Isthmus) operator fee formula:** `operatorFee = (gasUsed * operatorFeeScalar / 1e6) + operatorFeeConstant`
</Info>

## Parameters

All parameters live on the `SystemConfig` contract on L1 (see the [`ISystemConfig` interface](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/interfaces/L1/ISystemConfig.sol)).
Each getter below is a `view` method with the same name as the parameter.

| Parameter              | Type     | What it controls                                                                                                                                                                          | Setter                                 | OP Mainnet value       |
| ---------------------- | -------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------- | ---------------------- |
| `eip1559Denominator`   | `uint32` | EIP-1559 max-change denominator: appears in the denominator of the per-block base fee delta. Lower = faster base fee response, more volatility.                                           | `setEIP1559Params(uint32,uint32)`      | `250`                  |
| `eip1559Elasticity`    | `uint32` | Elasticity multiplier: sets the gas target relative to the gas limit (`gas_target = gasLimit / elasticity`). Larger elasticity = smaller target, so base fee increases sooner under load. | `setEIP1559Params(uint32,uint32)`      | `2`                    |
| `gasLimit`             | `uint64` | Maximum gas per block. Lower limit = less supply per block, making base fees more sensitive to demand.                                                                                    | `setGasLimit(uint64)`                  | `40,000,000`           |
| `minBaseFee`           | `uint64` | Minimum floor on the base fee, in wei (can be 0). See [setting the minimum base fee](/chain-operators/guides/features/setting-min-base-fee).                                              | `setMinBaseFee(uint64)`                | `0`                    |
| `basefeeScalar`        | `uint32` | Scales the `l1BaseFee` (per-byte) contribution to the L1 data fee.                                                                                                                        | `setGasConfigEcotone(uint32,uint32)`   | `5227`                 |
| `blobbasefeeScalar`    | `uint32` | Scales the `l1BlobBaseFee` (per-blob) contribution to the L1 data fee.                                                                                                                    | `setGasConfigEcotone(uint32,uint32)`   | `1014213`              |
| `operatorFeeScalar`    | `uint32` | Per-gas operator margin. See [setting the operator fee](/chain-operators/guides/features/setting-operator-fee).                                                                           | `setOperatorFeeScalars(uint32,uint64)` | `0`                    |
| `operatorFeeConstant`  | `uint64` | Flat per-transaction operator fee, in wei.                                                                                                                                                | `setOperatorFeeScalars(uint32,uint64)` | `0`                    |
| `daFootprintGasScalar` | `uint16` | Scales estimated DA usage to the gas dimension to limit DA-heavy blocks. See [how the DA footprint block limit works](/chain-operators/reference/da-footprint).                           | `setDAFootprintGasScalar(uint16)`      | `0` (treated as `400`) |

<Warning>
  * Any non-zero operator fee makes the chain configuration [non-standard](/chain-operators/reference/standard-configuration).
  * A `daFootprintGasScalar` of `0` is treated as the default of `400`; set it to `1` to effectively disable the DA footprint limit.
</Warning>

The OP Mainnet values can be verified against the [OP Mainnet SystemConfig contract on Etherscan](https://etherscan.io/address/0x229047fed2591dbec1eF1118d64F7aF3dB9EB290#readProxyContract).

## Fee vault recipients

Fees are gathered in dedicated contract [fee vaults](/op-stack/transactions/fee-vaults). See the [fee vault operations guide](/chain-operators/guides/management/fee-vaults) for how to manage and withdraw from these vaults.

| Fee component | Recipient vault     |
| ------------- | ------------------- |
| `baseFee`     | `BaseFeeVault`      |
| `priorityFee` | `SequencerFeeVault` |
| `l1Fee`       | `L1FeeVault`        |
| `operatorFee` | `OperatorFeeVault`  |

## Reading current values

Each parameter has a getter with the same name on the `SystemConfig` contract:

```bash theme={null}
export L1_RPC=<L1_RPC>
export SYSTEM_CONFIG=<SYSTEM_CONFIG_ADDRESS>

cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "eip1559Denominator()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "eip1559Elasticity()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "gasLimit()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "minBaseFee()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "basefeeScalar()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "blobbasefeeScalar()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "operatorFeeScalar()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "operatorFeeConstant()"
cast call --rpc-url $L1_RPC $SYSTEM_CONFIG "daFootprintGasScalar()"
```

## References

* [Transaction fees on OP Mainnet](https://docs.optimism.io/op-stack/transactions/fees#transaction-fees-on-op-mainnet)
* [Operator fee](https://docs.optimism.io/op-stack/transactions/fees#operator-fee)
* [L1 data fee](https://docs.optimism.io/op-stack/transactions/fees#l1-data-fee)
* [`ISystemConfig` interface](https://github.com/ethereum-optimism/optimism/blob/develop/packages/contracts-bedrock/interfaces/L1/ISystemConfig.sol)
* [DA footprint](https://docs.optimism.io/notices/archive/upgrade-17#block-header-changes)
* [EIP-1559 parameters](https://docs.optimism.io/op-stack/protocol/differences#eip-1559-parameters)