Transaction Fees

Transactions on Liberty Chain cost a fraction of what they would on Ethereum mainnet. Typical transactions cost between $0.001 and $0.01, making on-chain operations economically viable for high-frequency use cases like trading, settlement, and compliance checks.

This page explains how fees are calculated, what drives costs, and how to estimate gas for your transactions.

Fee Structure

Every transaction on Liberty Chain pays two fees:

L2 Execution Fee

The L2 execution fee covers the cost of executing your transaction on Liberty Chain. It works the same way as gas on Ethereum: the fee is calculated as the gas used multiplied by the current gas price.

The L2 gas price on Liberty Chain is significantly lower than Ethereum because the chain has much higher throughput and lower contention. The gas used for a given operation is identical to Ethereum — a simple ETH transfer uses 21,000 gas, an ERC-20 transfer uses approximately 65,000 gas, and so on.

L1 Data Fee

The L1 data fee covers the cost of posting your transaction data to Ethereum L1 for data availability. This is typically the larger component of the total fee. The cost depends on the size of the transaction data (in bytes) and the current Ethereum L1 gas price.

The L1 data fee fluctuates with Ethereum L1 gas prices. When L1 is congested, L2 fees increase slightly. With EIP-4844 blob data, L1 data costs are dramatically lower than using calldata, keeping Liberty Chain fees consistently low.

Typical Costs

The following table shows approximate costs for common operations on Liberty Chain. Actual costs depend on L1 gas prices at the time of the transaction.

Estimating Gas

Use the eth_estimateGas RPC method to estimate how much gas a transaction will consume. This returns the L2 execution gas only — the L1 data fee is calculated separately and added automatically.

curl -X POST https://testnet-rpc.lcx.com \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [{
      "from": "0xYOUR_ADDRESS",
      "to": "0xRECIPIENT_ADDRESS",
      "value": "0xde0b6b3a7640000"
    }],
    "id": 1
  }'

In JavaScript with ethers.js:

import { ethers } from "ethers";

const provider = new ethers.JsonRpcProvider(
  "https://testnet-rpc.lcx.com"
);

// Estimate gas for a simple transfer
const gasEstimate = await provider.estimateGas({
  from: "0xYOUR_ADDRESS",
  to: "0xRECIPIENT_ADDRESS",
  value: ethers.parseEther("0.1"),
});
console.log("Estimated gas:", gasEstimate.toString());

// Get current fee data
const feeData = await provider.getFeeData();
console.log("Gas price:", ethers.formatUnits(feeData.gasPrice, "gwei"), "gwei");

// Calculate L2 execution cost
const l2Cost = gasEstimate * feeData.gasPrice;
console.log("L2 execution cost:", ethers.formatEther(l2Cost), "ETH");

Querying the GasPriceOracle

For advanced use cases, you can query the GasPriceOracle system contract directly to read fee parameters:

import { ethers } from "ethers";

const provider = new ethers.JsonRpcProvider(
  "https://testnet-rpc.lcx.com"
);

const ORACLE_ADDRESS = "0x420000000000000000000000000000000000000F";
const ORACLE_ABI = [
  "function l1BaseFee() view returns (uint256)",
  "function baseFee() view returns (uint256)",
  "function gasPrice() view returns (uint256)",
  "function getL1Fee(bytes) view returns (uint256)",
];

const oracle = new ethers.Contract(ORACLE_ADDRESS, ORACLE_ABI, provider);

const l1BaseFee = await oracle.l1BaseFee();
console.log("L1 base fee:", ethers.formatUnits(l1BaseFee, "gwei"), "gwei");

// Estimate L1 data fee for a specific transaction
const txData = "0x..."; // raw transaction bytes
const l1Fee = await oracle.getL1Fee(txData);
console.log("L1 data fee:", ethers.formatEther(l1Fee), "ETH");

Tips for Minimizing Fees

• Reduce calldata size — the L1 data fee scales with transaction data size. Use smaller function signatures, pack data efficiently, and avoid unnecessary bytes in your transactions.
• Batch operations — if your contract supports it, batch multiple operations into a single transaction to amortize the L1 data fee across more work.
• Use events for data — emit events instead of storing rarely-accessed data in contract storage. Events are much cheaper than storage writes.
• Monitor L1 gas prices — if your use case is not time-sensitive, submit transactions when L1 gas prices are lower (typically weekends and off-peak hours) for lower L1 data fees.

Related Pages

• Architecture — understand why the two-fee model exists and how data flows from L2 to L1.
• RPC API Reference — full reference for eth_estimateGas, eth_gasPrice, and related methods.
• Network Details — system contract addresses including the GasPriceOracle.