Estimating gas before sending prevents both failed transactions (limit too low) and overpaying (limit or price too high); most SDKs expose an estimate that the UI should pad slightly for safety.
function estimateWithBuffer(estimatedGas: bigint, bufferPercent = 20): bigint {
return estimatedGas + (estimatedGas * BigInt(bufferPercent)) / 100n;
}
function totalFeeWei(gasLimit: bigint, gasPriceWei: bigint): bigint {
return gasLimit * gasPriceWei;
}Showing the fee in both native token and an approximate fiat value (using a cached price, clearly marked as an estimate) helps users judge whether a transaction is worth its cost before confirming.