# Is there a max amount of gas per transaction?

If there's an ICO with a cap of \$1 million usd and there's \$10 million Ether being sent all at the same time, I'm assuming the transaction with the highest gas gets prioritized...but is there a limit to how much gas you can put? For example will 500,000,000 gas get rejected by the miners?

Edit 1/2019: ~8 mil. gas limit

Edit 1/2020: ~10 mil. gas limit

Edit 10/2021: ~30 mil. gas limit

Edit 11/2022: ~30 mil. gas limit

There is a dynamic block gas limit. You can look it up here: https://etherscan.io/blocks

It does not matter how much gas you send along, as the unused will be returned to you anyway. What matters, though, is the price you offer, which has no limit. Of course, you must be able to pay the total sum.

• E.g. a gas price of 4.5 trillion and a gas limit of 2 million would be okay? And what would happen if I put a gas limit over 4,3 million? Thank you so much!
– ello
May 29, 2017 at 19:24
• Nothing would happen, you'd still pay 23000 gas * 4.5 trillion Wei for one transaction. Do not mix up gas limit with block gas limit. Gas limit in transaction defines the maximum amount of gas you send along for the transaction to be consumed, the unused amount will be returned. the block gas limit means the maximum total amount of gas usage to be included in one block. So if there would be Y transactions at the same time, whose consumed gas just fits the blockgas limit, the transaction Y+1 , exceeding the block gas limit, would not be included in that block.
– n1cK
May 29, 2017 at 19:36
• So a gas limit too high will reduce the chances of being included in a block? Before the ICO you don't know how much you need...e.g. 200k or 400k
– ello
May 29, 2017 at 20:49
• Let me put it this way: Things happening at ICOs are only loosely related to gas limits and total transaction values. A rule of thumb would be: If you are able to answer 20 questions in this board, you are ready to do an ICO ;) but seriously, don't be discouraged learning and understanding Ethereum. 0x3574ef99c637D09aFcc474bb67fe2C96A39722cB , thank you.
– n1cK
May 30, 2017 at 9:24
• You are already in 2020 ? Where are you ? :O Dec 27, 2019 at 14:53

Gas limit per transaction is in theory the same as block gas limit (if the block was only to fit 1 transaction). And it is a dynamic limit.

A convenient way to look it up is visiting https://etherscan.io/blocks selecting the latest block, and see value in "Gas Limit:"

• Update May 2024: it seems to be now fixed at 30M limit for Ethereum. Still consider it will change in the future. May 7 at 19:46
• Max gas limit for a transaction is the gas limit for that particular block.
• you can get the gas limit of block by eth.getBlock('latest') and checking gasLimit parameter in it.
• gas limit of the next block is 1.2 times of the moving avg of gas limit of all previous blocks.

so. maximum gas limit upcoming transactions approximately equals (1.2 times avg gas-limit)