An estimate is a simulation result
eth_estimateGas estimates the gas needed for a call against a particular state. A receipt reports what a later included transaction actually used. State changes, execution paths and call-gas forwarding can make those values differ. The estimate is not a promise about the final fee.
Keep the request identical
{"jsonrpc":"2.0","id":1,"method":"eth_estimateGas","params":[{"from":"SENDER","to":"CONTRACT","value":"0x0","data":"CALLDATA"}]}Use the same sender, value and calldata as the transaction you intend to sign. A sender-dependent contract may take a different path when the sender is omitted. Save the request and returned estimate so a later receipt can be compared meaningfully.
Compare the right fields
- Read the receipt status before interpreting gas use. A reverted transaction also consumes gas.
- Compare gasUsed with the gas limit, not with the account's total ETH balance change.
- Separate execution cost from other fee components and transferred value.
- For Robinhood Chain, follow its L2 fee model, which also accounts for data posted to Ethereum.
Set a deliberate policy
Use a bounded safety margin appropriate to the application, then simulate again if state is likely to have changed. A larger gas limit does not repair invalid calldata, missing allowance or a contract revert. EIP-150's call forwarding rule can also mean a transaction needs available gas above the amount ultimately spent. Keep fee affordability and execution feasibility as separate checks.