A gas limit is the most gas you allow a transaction to use. It is not an amount of money. Gas measures computational work. What you pay is the gas actually used multiplied by the price per unit of gas. Any gas you allow but don't use is returned to you. A standard ETH transfer needs a limit of 21,000 gas. Smart contract calls need more, and how much depends on what the contract does. Your wallet usually estimates the limit for you.
Ethereum also has a second gas limit, for whole blocks. As of 25 October 2026 the default block gas limit on mainnet is 60 million gas, set by the Fusaka upgrade on 3 December 2025. A planned raise toward roughly 200 million is being tested under the next upgrade, Glamsterdam. It has no mainnet date.
Gas, gas limit and gas price: the three terms
Gas
ethereum.org defines gas as "the unit that measures the amount of computational effort required to execute specific operations" on Ethereum. Each operation costs a fixed amount of gas, so a more complex transaction uses more gas.
Gas limit (per transaction)
This is "the maximum amount of gas you are willing to consume on a transaction" (ethereum.org). It caps the work, not the price.
Gas price: base fee and priority fee
Since EIP-1559, the price per unit of gas has two parts:
- Base fee. The protocol sets it for each block, and it is burned. EIP-1559 says "the base fee is always burned (i.e. it is destroyed by the protocol)". It moves by at most one-eighth (12.5%) per block, depending on whether the previous block used more or less gas than the target.
- Priority fee (tip). This goes to the validator who includes your transaction. You set it with
max_priority_fee_per_gas.
You can also set max_fee_per_gas, the most you will pay per unit in total. Per the EIP-1559 specification, the price you actually pay is the base fee plus a tip, and the tip is capped so the total never exceeds your max fee. The difference between your max fee and what you actually paid is refunded.
How the fee is calculated
The formula from ethereum.org is:
fee = gas used × (base fee + priority fee)
ethereum.org's worked example: a 1 ETH transfer uses 21,000 gas, with a base fee of 10 gwei and a tip of 2 gwei.
| Item | Value |
|---|---|
| Gas used | 21,000 |
| Price per gas | 10 + 2 = 12 gwei |
| Total fee | 252,000 gwei = 0.000252 ETH |
| Burned (base fee) | 0.00021 ETH |
| To validator (tip) | 0.000042 ETH |
| Sender debited | 1.000252 ETH |
One gwei is one-billionth of an ETH.
The fee uses gas used, not the gas limit. ethereum.org gives an example: if you set a 50,000 limit on a simple transfer, 21,000 is used and 29,000 is returned. A high limit does not by itself make a transaction cost more.
What happens if the limit is wrong
Too low
There are two cases:
- Below the minimum a transaction needs. The network rejects it during validation, and no gas is consumed (ethereum.org).
- Enough to start, not enough to finish. Execution stops, and all state changes are reverted. But "all the gas provided will still be consumed for the work performed" (ethereum.org). You pay for a transaction that did nothing, and you have to send it again.
A lower limit never makes the work cheaper. The work needs the same amount of gas whatever limit you set.
Too high
Unused gas comes back, so a generous limit costs nothing extra. Since Fusaka, though, no transaction can use more than 16,777,216 gas (see below).
How wallets choose a limit
Wallets usually call the eth_estimateGas method, which "generates and returns an estimate of how much gas is necessary to allow the transaction to complete." The JSON-RPC documentation warns that the estimate "may be significantly more than the amount of gas actually used". That is expected, because the surplus is refunded.
What will this transaction cost in gas?
Enter the gas your transaction actually uses, the base fee and your tip to see the total fee in gwei.
| Gas actually used by the transaction | Base fee per unit of gas (burned) | Priority fee (tip) per unit of gas, paid to the validator | Total fee |
|---|---|---|---|
| 21,000 gas | 10 gwei | 2 gwei | 252,000 gwei |
| 21,000 gas | 20 gwei | 2 gwei | 462,000 gwei |
| 60,000 gas | 10 gwei | 2 gwei | 720,000 gwei |
- All three inputs are your own values. The defaults copy ethereum.org's worked example: 21,000 gas at 10 + 2 gwei gives 252,000 gwei, which is 0.000252 ETH.
- One gwei is one-billionth of an ETH. The base-fee share of the total is burned, and the tip share goes to the validator.
- The fee uses gas used, not the gas limit. A higher limit does not cost more on its own, because unused gas is refunded.
This multiplies your inputs and nothing more. It cannot predict the base fee of a future block, does not convert gwei to any currency, and does not cover a transaction that runs out of gas, where all the gas provided is still consumed.
The block gas limit
Every block also has a gas limit, which caps the total work in that block.
- Target and maximum. Under EIP-1559, each block aims to use half the limit, and blocks can grow up to twice the target. The base fee rises when blocks use more than the target and falls when they use less.
- Who sets it. ethereum.org says the block gas limit can change through validator signalling and through network upgrades.
- 2025. ethereum.org reports that the limit rose from 30 million to 60 million during 2025. Fusaka included EIP-7935, which "raises Ethereum's default gas limit to 60M" (Ethereum Foundation, Fusaka mainnet announcement).
Per-transaction cap since Fusaka (3 December 2025)
Fusaka went live on mainnet at epoch 411392 on 3 December 2025, 21:49:11 UTC. One of its core changes is EIP-7825. It caps gas per transaction at 16,777,216 (2^24), whatever the block limit is. A transaction with a higher gas limit is rejected, and a block that contains one is invalid. The EIP gives the reasons as lowering denial-of-service risk and keeping block validation times predictable, because "a single transaction consuming most or all of the block gas can result in uneven load distribution."
In practice, a contract deployment or batch call that needs more than about 16.78 million gas has to be split into several transactions.
Latest: Glamsterdam and the 200 million plan (October 2026)
- 6 October 2026. Glamsterdam went live on the Sepolia testnet at 13:53:36 UTC (Ethereum Foundation testnet announcement, 17 September 2026). That announcement says the Prysm 7.2.0 and Teku 26.9.1 clients still default to a 60M gas limit after activation, so validators have to configure 200M themselves.
- 8 October 2026. CoinDesk reported that Sepolia blocks were being produced with a limit near 200 million gas. Its review of more than 25 consecutive blocks found 52 million to 92 million gas used per block. This figure comes from CoinDesk alone.
- 16 October 2026. The Ethereum Foundation scheduled Glamsterdam on the Hoodi testnet for 26 October, with the gas limit rising to 200M at the same epoch.
- 22 October 2026. The Foundation postponed the Hoodi activation "to allow for further investigation of interactions of EIP-8037 with mainnet smart contracts." EIP-8037 raises the gas cost of creating state. The postponement also removed the schedule that would have taken Hoodi's gas limit to 200M. No new Hoodi date and no mainnet date have been set.
ethereum.org says Glamsterdam's two headline changes, Block-Level Access Lists (EIP-7928) and enshrined proposer-builder separation (EIP-7732), make it safe to raise the block gas limit "from 60 million today toward roughly 200 million." It presents this as a direction, not a fixed number. Its timing was "Activation is expected in the second half of 2026", written before the Hoodi delay.
What could change for individual transactions
Glamsterdam also reprices gas. EIP-2780 (resource-based intrinsic transaction gas) is in Last Call, with a deadline of 1 November 2026. It is not live on mainnet. As drafted:
Time left until 1 November 2026 · end of day UTC
- A plain ETH transfer to an existing account stays at 21,000 gas.
- A zero-value transfer to an existing account would cost 15,000 gas.
- A value transfer that creates a new account would add 183,600 "state gas" on top of 21,000.
If these numbers ship, a transfer to a new address would need a much higher gas limit than 21,000. Wallet estimates would have to account for that.
Quick reference
| Question | Answer (as of 25 October 2026) |
|---|---|
| What is a gas limit? | The most gas a transaction may use; a cap on work, not on price |
| Plain ETH transfer | 21,000 gas |
| Unused gas | Refunded |
| Out of gas mid-execution | Changes reverted, gas still consumed |
| Max gas per transaction | 16,777,216 (EIP-7825, since 3 Dec 2025) |
| Default block gas limit | 60 million (EIP-7935, Fusaka) |
| Planned block limit | Toward ~200 million under Glamsterdam; testnet only, no mainnet date |
Limitations: the mainnet block limit can change through validator signalling, and the Glamsterdam figures may change before they reach mainnet.
