Gas Estimation

Overview

Accurate gas estimation is crucial for successful transaction execution. The OKX DEX SDK provides methods to estimate gas limits and retrieve current gas prices, including EIP-1559 support.

Gas Price Estimation

Get current gas prices for any supported chain.

Basic Gas Price

import { OKXDexClient } from '@okxweb3/dex-sdk';

const client = new OKXDexClient({
  apiKey: process.env.OKX_API_KEY!,
  secretKey: process.env.OKX_SECRET_KEY!,
  apiPassphrase: process.env.OKX_API_PASSPHRASE!,
  projectId: process.env.OKX_PROJECT_ID!
});

const gasPrice = await client.dex.getGasPrice('1'); // Ethereum mainnet
console.log('Gas price data:', gasPrice);

EIP-1559 Gas Pricing

For chains supporting EIP-1559 (Ethereum, Polygon, Base, etc.):

const gasPrice = await client.dex.getGasPrice('8453'); // Base

if (gasPrice.data[0]) {
  const { baseFee, maxFeePerGas, maxPriorityFeePerGas } = gasPrice.data[0];
  
  console.log('Base Fee:', baseFee);
  console.log('Max Fee Per Gas:', maxFeePerGas);
  console.log('Max Priority Fee:', maxPriorityFeePerGas);
  
  // Calculate total cost
  const estimatedGasLimit = 200000;
  const maxCost = BigInt(maxFeePerGas) * BigInt(estimatedGasLimit);
  console.log('Max transaction cost:', maxCost.toString(), 'wei');
}

EIP-1559 uses a base fee (burned) + priority fee (to validators) model. The maxFeePerGas includes both components.

Gas Limit Estimation

Estimate the gas required for a specific transaction.

Get Swap Transaction Data

First, get the transaction data from a swap quote:

import { ethers } from 'ethers';
import { createEVMWallet } from '@okxweb3/dex-sdk';

const provider = new ethers.JsonRpcProvider(process.env.EVM_RPC_URL!);
const evmWallet = createEVMWallet(process.env.EVM_PRIVATE_KEY!, provider);

const client = new OKXDexClient({
  apiKey: process.env.OKX_API_KEY!,
  secretKey: process.env.OKX_SECRET_KEY!,
  apiPassphrase: process.env.OKX_API_PASSPHRASE!,
  projectId: process.env.OKX_PROJECT_ID!,
  evm: { wallet: evmWallet }
});

const swapData = await client.dex.getSwapData({
  chainIndex: '8453',
  fromTokenAddress: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE', // ETH
  toTokenAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',   // USDC
  amount: '100000000000000000', // 0.1 ETH
  slippagePercent: '0.05',
  userWalletAddress: evmWallet.address
});

const txData = swapData.data[0]?.tx;
console.log('Transaction gas from swap data:', txData?.gas);

Estimate Gas Limit

Use the transaction data to get a precise gas estimate:

if (txData && txData.data) {
  const gasLimit = await client.dex.getGasLimit({
    chainIndex: '8453',
    fromAddress: txData.from,
    toAddress: txData.to,
    txAmount: txData.value,
    extJson: {
      inputData: txData.data  // Transaction calldata
    }
  });
  
  console.log('Estimated gas limit:', gasLimit.data[0]?.gasLimit);
}

Simple ETH Transfer

const gasLimit = await client.dex.getGasLimit({
  chainIndex: '1',
  fromAddress: '0x742d35Cc6634C0532925a3b844Bc9e7595f0bEb',
  toAddress: '0x1234567890123456789012345678901234567890',
  txAmount: '1000000000000000000' // 1 ETH
});

console.log('Gas limit for ETH transfer:', gasLimit.data[0]?.gasLimit);

Contract Interaction

const gasLimit = await client.dex.getGasLimit({
  chainIndex: '8453',
  fromAddress: evmWallet.address,
  toAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913', // Contract address
  txAmount: '0',
  extJson: {
    inputData: '0xa9059cbb...' // Contract call data
  }
});

console.log('Gas limit for contract call:', gasLimit.data[0]?.gasLimit);

Complete Gas Estimation Example

import { OKXDexClient } from '@okxweb3/dex-sdk';
import { ethers } from 'ethers';
import { createEVMWallet } from '@okxweb3/dex-sdk';

const provider = new ethers.JsonRpcProvider(process.env.EVM_RPC_URL!);
const evmWallet = createEVMWallet(process.env.EVM_PRIVATE_KEY!, provider);

const client = new OKXDexClient({
  apiKey: process.env.OKX_API_KEY!,
  secretKey: process.env.OKX_SECRET_KEY!,
  apiPassphrase: process.env.OKX_API_PASSPHRASE!,
  projectId: process.env.OKX_PROJECT_ID!,
  evm: { wallet: evmWallet }
});

async function estimateSwapGas() {
  try {
    const chainIndex = '8453'; // Base
    
    // Step 1: Get current gas prices
    console.log('=== Current Gas Prices ===');
    const gasPrice = await client.dex.getGasPrice(chainIndex);
    
    const { baseFee, maxFeePerGas, maxPriorityFeePerGas } = gasPrice.data[0];
    console.log('Base Fee:', baseFee, 'wei');
    console.log('Max Fee Per Gas:', maxFeePerGas, 'wei');
    console.log('Max Priority Fee:', maxPriorityFeePerGas, 'wei');
    
    // Step 2: Get swap transaction data
    console.log('\n=== Getting Swap Data ===');
    const swapData = await client.dex.getSwapData({
      chainIndex,
      fromTokenAddress: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
      toTokenAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
      amount: '100000000000000000', // 0.1 ETH
      slippagePercent: '0.05',
      userWalletAddress: evmWallet.address
    });
    
    const txData = swapData.data[0]?.tx;
    console.log('Suggested gas from API:', txData?.gas);
    
    // Step 3: Estimate gas limit
    if (txData && txData.data) {
      console.log('\n=== Gas Limit Estimation ===');
      const gasLimit = await client.dex.getGasLimit({
        chainIndex,
        fromAddress: txData.from,
        toAddress: txData.to,
        txAmount: txData.value,
        extJson: {
          inputData: txData.data
        }
      });
      
      const estimatedGasLimit = gasLimit.data[0]?.gasLimit;
      console.log('Estimated gas limit:', estimatedGasLimit);
      
      // Step 4: Calculate total cost
      console.log('\n=== Cost Estimation ===');
      const maxCost = BigInt(maxFeePerGas) * BigInt(estimatedGasLimit || txData.gas);
      const maxCostInEth = Number(maxCost) / 1e18;
      
      console.log('Max transaction cost:', maxCost.toString(), 'wei');
      console.log('Max transaction cost:', maxCostInEth.toFixed(6), 'ETH');
      
      // With priority fee only
      const likelyCost = (BigInt(baseFee) + BigInt(maxPriorityFeePerGas)) * BigInt(estimatedGasLimit || txData.gas);
      const likelyCostInEth = Number(likelyCost) / 1e18;
      console.log('Likely transaction cost:', likelyCostInEth.toFixed(6), 'ETH');
    }
  } catch (error) {
    console.error('Error:', error);
  }
}

estimateSwapGas();

Using Swap Data Gas Estimates

The getSwapData method already includes gas estimates:

const swapData = await client.dex.getSwapData({
  chainIndex: '8453',
  fromTokenAddress: '0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE',
  toTokenAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
  amount: '100000000000000000',
  slippagePercent: '0.05',
  userWalletAddress: evmWallet.address
});

const tx = swapData.data[0]?.tx;

// Gas data is included in the response
console.log('Gas limit:', tx.gas);
console.log('Gas price:', tx.gasPrice);
console.log('Max fee per gas:', tx.maxFeePerGas);
console.log('Max priority fee:', tx.maxPriorityFeePerGas);

// You can use these values directly
const transaction = {
  to: tx.to,
  value: tx.value,
  data: tx.data,
  gasLimit: tx.gas,
  maxFeePerGas: tx.maxFeePerGas,
  maxPriorityFeePerGas: tx.maxPriorityFeePerGas
};

The SDK automatically includes appropriate gas estimates in swap transaction data. You can use these values directly or verify them with getGasLimit.

Gas Optimization Tips

Add Safety Buffer

Always add a buffer to gas estimates:

const estimatedGas = gasLimit.data[0]?.gasLimit;
const gasWithBuffer = BigInt(estimatedGas) * BigInt(120) / BigInt(100); // 20% buffer

console.log('Gas with 20% buffer:', gasWithBuffer.toString());

EIP-1559 Priority Fees

Adjust priority fees based on urgency:

const gasPrice = await client.dex.getGasPrice('1');
const basePriorityFee = BigInt(gasPrice.data[0].maxPriorityFeePerGas);

// Low priority (slow)
const lowPriorityFee = basePriorityFee * BigInt(80) / BigInt(100);

// Standard priority
const standardPriorityFee = basePriorityFee;

// High priority (fast)
const highPriorityFee = basePriorityFee * BigInt(150) / BigInt(100);

console.log('Low priority fee:', lowPriorityFee.toString());
console.log('Standard priority fee:', standardPriorityFee.toString());
console.log('High priority fee:', highPriorityFee.toString());

Monitor Gas Prices

For time-sensitive transactions, monitor gas prices:

async function waitForLowerGas(maxGwei: number) {
  while (true) {
    const gasPrice = await client.dex.getGasPrice('1');
    const currentGwei = Number(gasPrice.data[0].maxFeePerGas) / 1e9;
    
    console.log(`Current gas: ${currentGwei.toFixed(2)} gwei`);
    
    if (currentGwei <= maxGwei) {
      console.log('Gas price acceptable, proceeding...');
      break;
    }
    
    console.log(`Waiting for gas below ${maxGwei} gwei...`);
    await new Promise(resolve => setTimeout(resolve, 30000)); // Check every 30s
  }
}

await waitForLowerGas(20); // Wait for gas below 20 gwei

Chain-Specific Considerations

Ethereum Mainnet

High gas costs during peak hours
Use EIP-1559 for better estimates
Consider L2 alternatives

const gasPrice = await client.dex.getGasPrice('1');
const currentGwei = Number(gasPrice.data[0].maxFeePerGas) / 1e9;

if (currentGwei > 50) {
  console.warn('Gas prices are high. Consider using L2 or waiting.');
}

Layer 2 Networks (Base, Arbitrum, Optimism)

Significantly lower gas costs
Faster confirmation times
Still use EIP-1559

// Base typically has very low gas
const baseGasPrice = await client.dex.getGasPrice('8453');
console.log('Base gas price:', baseGasPrice.data[0].maxFeePerGas);

BSC and Polygon

Lower gas costs than Ethereum
May use legacy gas pricing or EIP-1559

const bscGasPrice = await client.dex.getGasPrice('56');
const polygonGasPrice = await client.dex.getGasPrice('137');

API Reference

getGasPrice

Parameters:

chainIndex - Chain identifier (e.g., ‘1’ for Ethereum, ‘8453’ for Base)

Returns:

baseFee - Current base fee (EIP-1559 chains)
maxFeePerGas - Maximum fee per gas unit
maxPriorityFeePerGas - Maximum priority fee per gas
gasPrice - Legacy gas price (non-EIP-1559 chains)

getGasLimit

Parameters:

chainIndex - Chain identifier
fromAddress - Sender address
toAddress - Recipient or contract address
txAmount - Transaction value in wei
extJson - Extended JSON with optional inputData for contract calls

Returns:

gasLimit - Estimated gas limit for the transaction

Next Steps

Transaction Broadcasting

Broadcast transactions with optimal gas settings

Executing Swaps

Execute swaps with proper gas configuration

Get Started

Core Concepts

Guides

Advanced Features

Overview

Gas Price Estimation

Basic Gas Price

EIP-1559 Gas Pricing

Gas Limit Estimation

Simple ETH Transfer

Contract Interaction

Complete Gas Estimation Example

Using Swap Data Gas Estimates

Gas Optimization Tips

Add Safety Buffer

EIP-1559 Priority Fees

Monitor Gas Prices

Chain-Specific Considerations

Ethereum Mainnet

Layer 2 Networks (Base, Arbitrum, Optimism)

BSC and Polygon

API Reference

getGasPrice

getGasLimit

Next Steps

Transaction Broadcasting

Executing Swaps

Build docs developers (and LLMs) love

Get Started

Core Concepts

Guides

Advanced Features

​Overview

​Gas Price Estimation

​Basic Gas Price

​EIP-1559 Gas Pricing

​Gas Limit Estimation

​Simple ETH Transfer

​Contract Interaction

​Complete Gas Estimation Example

​Using Swap Data Gas Estimates

​Gas Optimization Tips

​Add Safety Buffer

​EIP-1559 Priority Fees

​Monitor Gas Prices

​Chain-Specific Considerations

​Ethereum Mainnet

​Layer 2 Networks (Base, Arbitrum, Optimism)

​BSC and Polygon

​API Reference

​getGasPrice

​getGasLimit

​Next Steps

Transaction Broadcasting

Executing Swaps

Build docs developers (and LLMs) love

Overview

Gas Price Estimation

Basic Gas Price

EIP-1559 Gas Pricing

Gas Limit Estimation

Simple ETH Transfer

Contract Interaction

Complete Gas Estimation Example

Using Swap Data Gas Estimates

Gas Optimization Tips

Add Safety Buffer

EIP-1559 Priority Fees

Monitor Gas Prices

Chain-Specific Considerations

Ethereum Mainnet

Layer 2 Networks (Base, Arbitrum, Optimism)

BSC and Polygon

API Reference

getGasPrice

getGasLimit

Next Steps