Looking at the output of https://github.com/ethereum/wiki/wiki/JSON-RPC#eth_getblockbyhash

Does anyone know what do the "mixHash" and "extraData" field mean? and what is the Unit of gasLimit and gasUsed? (I think is GWei, but not sure)


2 Answers 2


gasLimit and gasUsed are denominated in a unit called gas. gasLimit is the maximum number of gas that the sender is willing to spend. gasUsed is the actual amount of gas consumed by the transaction.

To figure out how much the transaction cost in Wei you multiply gasPrice (another setting that the sender sets) by gasUsed.

gasUsed * gasPrice == cost of transaction in Wei.

  • so it is stored in "wei"? thats what Im looking to confirm. thanks
    – Diego
    Feb 12, 2018 at 20:00
  • 1
    Gas is in a unit called gas. It only becomes Wei when you multiply by price which is denominated in wei / gas. The gas units cancel out and you end up with Wei. Feb 12, 2018 at 20:33


A 256-bit hash which proves, combined with the nonce, that a sufficient amount of computation has been carried out on this block: the Proof-of-Work (PoF).


An optional free, but max. 32 byte long space to conserve smart things for ethernity on the Blockchain.


The gas limit is maximum amount of units of gas you are willing to spend on a transaction. This will decide by community based on your opcode set.

For example if you have a contract that will add two numbers, gasLimit maximum amount of units to execute function. This list will find below link


  • thanks. Regarding the gas, I want to know in what unit are the vales stored? wei, Gwei,...?
    – Diego
    Feb 12, 2018 at 20:01
  • As far as I know gas unit is gas. Gas will store in uint256 Feb 13, 2018 at 3:21

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