What mechanism lies behind adjusting the block gas limit dynamically?

Is it the miner that mined the most recent block who decides whether to adjust the gas limit or not?

How much can the block gas limit vary from block to block when adjusted?

1 Answer 1


The precise mechanism is defined in Ethereum's Yellow paper (PDF), subsection 4.3.4 Block header validity.

The miner of a new block can set the gas limit within +/- 0.1 % of the parent block's gas limit.

  • Why do I sometimes see, that authors write, that miners vote on whether to increase the block gas limit? Your answer tells me that it is, solely, the miner’s decision. +1.
    – Shuzheng
    Nov 25, 2017 at 7:44
  • In a sense this works as vote, those wanting to increase the gas limit will submit blocks with an increased gas limit, and those who oppose will submit blocks with decreasing gas limit. We can say the group with more blocks resolved will decide the final outcome.
    – Ismael
    Nov 25, 2017 at 15:31
  • I think it is hard to understand. Do the miner has any influence on the new block limit? For my perspective, it seems that if the block was mined "fast", the block limit increases, whereas it decreases if it is mined "slow".
    – Shuzheng
    Dec 23, 2017 at 14:25
  • @Shuzheng The Yellow paper defines a mechanism, increasing the difficulty, when blocks are found too quickly. The objective is to control issuance, but also controls how much gas is available for transactions. But lowering the average block time does increase the total available gas for transactions.
    – Ismael
    Dec 26, 2017 at 3:50
  • Why does lowering average block time increase total available gas for transactions? Aren’t block difficulty and block gas limit independent of each other?
    – Shuzheng
    Dec 26, 2017 at 8:32

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