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# System prepended metadata

title: Ethereum block limit

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# Ethereum block limit

The first crypto-currency Bitcion has limited a block size to 1-MB, and this is beacause if a block is too large it becomes expensive to store or sync with other nodes across the world or the blockchain.

Ethereum doesn't place a block limit like Bitcion does, it just limits the total amount of computation on a single block since each computation has a gas cost. And the reason for this is, if a block has too much computation on it, it becomes difficult for nodes to verify the transactions quickly. So with a block limit set, if a transactions requires too much gas the transactions gets reverted.

## What is gas?

Gas is a transaction unit that represents computational effort. It’s the fuel you must buy to get miners to add your transaction to a block.

At the time of writting the block limit is 30 million (30,000,000) gas; An eth transfer cost 21 thousand (21,000) gas, so doing the math you'd see that a single block can hold just 1,428 transfers approximately.

### A few relating terms.

- **Gas fee/price** is the amount of Ether (ETH) required for an Ethereum 
blockchain network user to conduct a transaction on the network. 
- **Gas fees** are used to compensate Ethereum miners for their work in verifying transactions and securing the network.
- **Gas limit** is maximum amount a person is willing to pay for a transaction to complete. keep in mind that more complicated transactions involving smart contracts require more computational work, so they require a higher gas limit than a simple payment. 
- **Gwei**: A fractional unit of ETH — 1.0 ETH = 1,000,000,000 Gwei (1 Gwei = 1 billionth of eth).
- **Transaction fee**: The fee associated with the completed transaction (gas used * gas price), which is then ollected by the miner who includes the transaction in a block.

> A standard ETH transfer requires a gas limit of 21,000 units of gas.


Need more info on gas, see [Ethereum docs](https://ethereum.org/en/developers/docs/gas/)

## Implications

There cannot be more than 1,428 transfers in one block, so if there are more people trying to make transfer, then this brings some form of competition in the play and rewarding anyone willing to pay more for their transaction to be added first; and this is why the gas price fluctuates.

This also affects smart contracts, if your contract takes more that 30 million gas then it can't fit into a block so it'd be reverted. So always keep in mind when writing a contract that if you write expensive code, it doesn't just affect your
users but the entire Ethereum network, because now they have to bid higher for their transactions to be added to a block in other words paying more gas.

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