Transaction Simulation

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Using simulate Directly

const gasEstimate = await client.simulate(address, messages, "optional memo");

import { calculateFee, GasPrice } from "@cosmjs/stargate";

const gasEstimate = await client.simulate(address, messages, memo);
const gasLimit = Math.ceil(gasEstimate * 1.5);
const fee = calculateFee(gasLimit, GasPrice.fromString("0.025uatom"));

const result = await client.signAndBroadcast(address, messages, fee, memo);

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How "auto" Uses Simulation

1. The transaction is built with an empty signature and sent to the chain’s Simulate endpoint
2. The chain executes it in a read-only context and returns gasUsed
3. The client multiplies by the gas multiplier (default 1.4x, or the value you passed)
4. calculateFee converts the gas limit to a StdFee using the configured gas price

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Caveats

• Simulation is an estimate. Actual gas can differ if chain state changes between simulation and execution.
• The multiplier buffer protects against this, but extremely volatile state (e.g. many concurrent transactions) may still cause out-of-gas errors.
• Simulation requires an RPC connection. Offline clients cannot simulate.