Ethereum gas fees explained: what you pay, why it changes, and how to pay less

If you’ve used Ethereum, you’ve paid gas: the fee for getting a transaction processed. Sometimes it’s tiny, sometimes it costs more than the thing you’re sending. Understanding how the fee is calculated makes it less mysterious, and helps you avoid paying more than you need to.

What gas is

ethereum.org defines gas as the unit that measures the computational effort required to carry out operations on the Ethereum network. Every action, from a simple ETH transfer to a trade on a decentralized exchange, needs a certain amount of gas.

Gas is priced in gwei: one gwei is one billionth of an ETH (0.000000001 ETH). So when a wallet shows a gas price of “10 gwei”, it means 10 billionths of an ETH per unit of gas.

Why charge at all? ethereum.org explains that requiring a fee for every computation stops bad actors from spamming the network, and that each transaction sets a limit on how much computation it can use.

How the fee is calculated

The formula from ethereum.org is:

gas used × (base fee + priority fee)

• Gas used: how much computation the transaction needs. A standard ETH transfer needs 21,000 gas. Interacting with smart contracts needs more.
• Base fee: set by the protocol for each block, and burned, meaning removed from circulation.
• Priority fee (tip): paid to the validator, as an incentive to include your transaction.

A worked example

These numbers are for illustration only. Suppose you send ETH (21,000 gas) when the base fee is 10 gwei and you add a 2 gwei tip:

• 21,000 × (10 + 2) = 252,000 gwei
• 252,000 gwei = 0.000252 ETH

The same transfer when the base fee is 50 gwei would cost 21,000 × 52 = 1,092,000 gwei, or about 0.0011 ETH. The amount of ETH you send doesn’t matter: sending 0.01 ETH or 100 ETH uses the same gas.

Why fees change

Each block has a target size of half the gas limit, but blocks can grow up to twice the target when demand is high. ethereum.org explains that the base fee adjusts by up to 12.5% per block depending on whether the previous block was above or below the target.

In practice:

• When many people want to transact at once, blocks fill up and the base fee climbs.
• When the network is quiet, blocks are less full and the base fee falls.

How fast the base fee can climb

ethereum.org illustrates the rule with a table, using a block gas limit of 36 million and a starting base fee of 100 gwei. If every block after the first is completely full, the base fee rises 12.5% per block:

Two practical consequences, according to ethereum.org:

• Because the maximum rise is fixed, your wallet knows for certain the highest base fee the next block can have: the current one × 112.5%.
• The fee grows so quickly that long runs of full blocks are unlikely: sooner or later, transactions stop being worth sending at that price and demand drops back.

Since the Fusaka upgrade in December 2025, Ethereum’s default block gas limit is 60 million, so the target is 30 million. See Ethereum’s upgrades explained.

Why fees sometimes get very high

ethereum.org gives two reasons. When demand is high, users offer higher tips to outbid each other and get into the next block. And complex smart contract apps may perform many operations, consuming a lot of gas per transaction.

Max fee and gas limit

Wallets usually set these for you, but it helps to know what they mean:

• Max fee: the most you’re willing to pay per unit of gas. ethereum.org says you’re refunded the difference between the max fee and the base fee plus tip actually charged.
• Gas limit: the most gas you’re willing to use on the transaction. If it’s too low to even start, the transaction is rejected before it’s included in a block and no gas is used. If it runs out during execution, the changes are reverted, but the gas is still consumed.

That’s why ethereum.org stresses that gas is paid whether a transaction succeeds or fails. A failed smart contract interaction can cost you the fee and achieve nothing.

How to pay less

1. Pick a quieter time. Because the base fee follows demand, the same transaction can cost much less when the network is less busy. Many wallets show the current base fee before you confirm.
2. Don’t overpay the tip. The wallet’s suggested priority fee is usually enough for normal transactions.
3. Use a layer 2 network. ethereum.org calls layer 2 scaling a primary way to improve gas costs. These networks, often called rollups, process transactions separately and store their data on Ethereum. Fees there are usually far lower.
4. Avoid failed transactions. Double-check addresses, amounts and approvals before you sign, and keep enough ETH for the fee.
5. Batch your moves. Fewer, larger transfers pay fewer network fees than many small ones.

A note on layer 2 safety

ethereum.org says the safety of layer 2 networks depends on their technology, smart contract security and maturity, and recommends due diligence, starting with small transactions. Always check which network you’re on and which network the recipient uses. See how to send crypto safely.

Paying gas without holding ETH

Normally you need ETH in your wallet to pay gas, even to send a stablecoin or an NFT. That’s starting to change:

• ethereum.org explains that smart contract wallets can let applications pay users’ gas fees, or let users pay in tokens other than ETH, removing the need to keep an ETH balance.
• Ethereum’s Pectra upgrade (May 2025) added gas sponsorship for ordinary accounts, through EIP-7702.

If an app offers to cover your gas, read what you’re being asked to sign: these features work through permissions on your account. See token approvals and how to revoke them.

Gas on layer 2 networks

Layer 2 networks charge their own, usually much lower, fees. They in turn pay Ethereum to post their data, which ethereum.org describes as two bills: a blob fee for the data and the execution gas needed to process it. That’s why the upgrades that made blob space cheaper, Dencun in 2024 and Fusaka in 2025, were aimed at lowering fees for layer 2 users. See what is a layer 2?

Exchange fees aren’t gas fees

When you withdraw ETH or tokens from an exchange, you usually pay the exchange’s withdrawal fee, which may differ from the network’s gas cost at that moment. Compare them before moving funds. See exchange fees explained.

Gas and tax

Paying gas means spending a small amount of ETH. In the US, for example, the IRS says moving crypto between your own wallets isn’t a taxable event, except for any crypto used to pay transaction fees. Keep your wallet history: fees also matter when working out the cost of what you buy and sell. See US crypto tax, UK crypto tax and Canada crypto tax.

For the bigger picture, see what is Ethereum? and bitcoin vs Ethereum.