Crypto gas fees explained: what you pay and how to pay less

Every transaction on a public blockchain pays a fee to the network that processes it. The fee rewards validators or miners and stops people from flooding the chain with junk transactions. It is paid in the chain's own coin, so an Ethereum fee is paid in ETH even if you are sending a stablecoin.

How Ethereum gas works

On Ethereum, "gas" measures how much computing work a transaction needs. A simple ETH transfer uses 21,000 gas; swapping tokens or minting an NFT uses more because the smart contract does more work.

Your fee is the gas used multiplied by the price per unit of gas, quoted in gwei (one gwei is a billionth of an ETH). Since the London upgrade in August 2021 (EIP-1559), that price has two parts:

• Base fee: set by the protocol for each block, rising when blocks are full and falling when they are not. The base fee is burned, so it is removed from circulation.
• Priority fee (tip): an extra amount you add to get picked up faster by validators.

Your wallet also sets a maximum fee. You never pay more than that cap, and you are only charged for the gas actually used. A transaction that fails still pays for the work done before it failed.

How Bitcoin fees work

Bitcoin fees depend on the size of the transaction in data, measured in virtual bytes, not on the amount sent. Wallets quote a rate in satoshis per virtual byte. Moving $10 or $10 million can cost the same fee if the transactions are the same size. When many people want to transact at once, the rate needed to get into the next block goes up.

Why fees spike

Block space is limited. During market crashes, popular token launches or NFT mints, many users compete for the same blocks and bid fees up. Fees can multiply within minutes and settle again once demand passes.

How to pay less

• Use a layer 2: rollups such as Arbitrum, Optimism and Base process transactions off the main chain and post them back in batches. Since Ethereum's Dencun upgrade in March 2024 cut the cost of posting that data, layer 2 fees are often a few cents. See how rollups batch transactions.
• Pick your moment: fees are usually lower when the network is quiet. Many wallets and block explorers show current fee levels.
• Batch and consolidate: fewer, larger transactions cost less in total than many small ones.
• Do not overpay the tip: for transactions that are not urgent, the wallet's standard setting is usually enough.

Watch out for

• Fake "gas fee" requests: no legitimate airdrop or support agent asks you to send crypto to pay a fee in advance.
• Approvals: signing a token approval also costs gas and can give a contract access to your tokens. Read what you sign; see our guide to .