Gas Limit
The gas limit in Ethereum and EVM-compatible networks is the maximum amount of computational work — measured in gas units — that a single transaction or an entire block may consume, serving as a cap that prevents computationally unbounded operations from halting the network and regulating throughput at the block level.
Gas is the unit that measures the computational effort required to execute a specific operation on the Ethereum Virtual Machine. Every EVM opcode has a fixed gas cost: a simple addition costs 3 gas, a storage write costs 20,000 gas, a transfer of Ether costs 21,000 gas. Complex smart contract interactions can consume millions of gas units.
The gas limit appears at two levels. At the transaction level, the sender specifies a maximum amount of gas they are willing to consume. If the transaction uses less, the remainder is refunded. If it hits the cap before completion, the transaction reverts and the gas consumed up to that point is not refunded — protecting the network from infinite loops while preventing the sender from losing their entire limit.
At the block level, the block gas limit is the ceiling on total gas all transactions in a block can collectively consume. Before EIP-1559, Ethereum miners voted to adjust the block gas limit slowly up or down. After EIP-1559, validators can raise or lower it by at most 1/1024 of the current limit per block, allowing gradual adjustment to network demand while preventing sudden capacity shocks.
The block gas limit is the primary lever for controlling Ethereum mainnet throughput. At a 30 million gas per block limit and a 12-second block time, Ethereum can process roughly 15-25 simple ETH transfers per second (or fewer, but more computationally intensive smart contract calls). Raising the gas limit increases throughput but increases the state growth rate and the computational burden on full nodes, potentially pricing out smaller node operators and reducing decentralization.
For layer-2 rollups, the effective gas limit per transaction is far higher because rollup execution happens off-chain. The rollup posts a compressed summary of hundreds or thousands of transactions to Ethereum as a single L1 transaction, dramatically increasing the effective throughput per unit of L1 gas consumed.
For U.S. users, the gas limit has practical implications for transaction cost estimation. When submitting a transaction to Ethereum, wallets typically auto-estimate the required gas, but setting the limit too low risks a failed transaction that still consumes gas fees. Understanding gas limit versus gas price is essential to managing on-chain transaction costs effectively.