How to Calculate Transaction Cost

Every transaction consumes compute units and requires a transaction fee in lamports to execute. The number of signatures included on a transaction determines the base transaction fee (5000 lamports per signature).

import {
 ComputeBudgetProgram,
 Connection,
 Keypair,
 LAMPORTS_PER_SOL,
 SystemProgram,
 TransactionMessage,
 VersionedTransaction
} from "openverse-web3";

// Connect to Openverse network
const connection = new Connection("https://api.devnet.openverse.network", "confirmed");

const { blockhash, lastValidBlockHeight } =
await connection.getLatestBlockhash();

// Create keypairs for transaction
const sender = Keypair.generate();
const recipient = Keypair.generate();
console.log(`Created sender account: ${sender.publicKey.toString()}`);
console.log(`Created recipient account: ${recipient.publicKey.toString()}`);

// Request and confirm airdrop
const airdropSignature = await connection.requestAirdrop(
 sender.publicKey,
 LAMPORTS_PER_SOL
);

await connection.confirmTransaction({
 signature: airdropSignature,
 blockhash,
 lastValidBlockHeight
});

// Create a transfer instruction
const transferInstruction = SystemProgram.transfer({
 fromPubkey: sender.publicKey,
 toPubkey: recipient.publicKey,
 lamports: 1000000 // 0.001 SOL
});

// Create simulation instructions with placeholder compute unit limit
const simulationInstructions = [
 ComputeBudgetProgram.setComputeUnitLimit({
   units: 1_400_000 // High value for simulation
 }),
 ComputeBudgetProgram.setComputeUnitPrice({
   microLamports: 1n
 }),
 transferInstruction
];

// Create transaction for simulation
const simulationTransaction = new VersionedTransaction(
 new TransactionMessage({
   instructions: simulationInstructions,
   payerKey: sender.publicKey,
   recentBlockhash: blockhash
 }).compileToV0Message()
);

// Simulate transaction to get compute unit estimate
const simulationResponse = await connection.simulateTransaction(
 simulationTransaction
);

const estimatedUnits = simulationResponse.value.unitsConsumed;
console.log(`Estimated compute units: ${estimatedUnits}`);

// Create final transaction with compute budget instructions
const computeUnitLimitInstruction = ComputeBudgetProgram.setComputeUnitLimit({
 units: estimatedUnits!
});

const computeUnitPriceInstruction = ComputeBudgetProgram.setComputeUnitPrice({
 microLamports: 1n
});

// Build transaction with all instructions
const messageV0 = new TransactionMessage({
 payerKey: sender.publicKey,
 recentBlockhash: blockhash,
 instructions: [
   computeUnitPriceInstruction,
   computeUnitLimitInstruction,
   transferInstruction
 ]
}).compileToV0Message();

// Calculate fee
const fees = await connection.getFeeForMessage(messageV0);
console.log(`Transaction fee: ${fees.value} lamports`);

const transaction = new VersionedTransaction(messageV0);
transaction.sign([sender]);

// Send and confirm transaction
const signature = await connection.sendTransaction(transaction);
console.log(`Transaction Signature: ${signature}`);