Gas Fee
Gas · Network fee · Transaction fee · Miner fee · Ethereum gas fee
The fee paid to a blockchain to record a transfer or run a contract, set by the computation used and network congestion, not by the amount sent.
Simple explanation
Background: Koreans say 가스비 ("gas fee") for almost any blockchain's network fee, not only Ethereum's. Customers of Korean exchanges never pay it directly; it reaches them inside each exchange's fixed withdrawal fee.
To get anything recorded on a blockchain you pay the party that builds blocks (a validator or miner). Ethereum calls one unit of computation "gas", hence "gas fee". It is an Ethereum term at heart, but in Korea it is used loosely for the transfer fees of other chains such as Bitcoin, Solana and Tron too. The fee has nothing to do with the amount sent: sending ₩10,000 or ₩1 billion takes the same computation for the same kind of transfer.
On Ethereum the fee is gas used × the price per unit of gas. Gas prices are quoted in gwei, and 1 gwei is 0.000000001 ETH (a billionth of an ether). The price per unit is the base fee, set by the network, plus a priority fee (a tip) offered to validators to get included sooner. A plain ETH transfer uses 21,000 gas. Sending a token or running a smart contract for DeFi or NFTs takes more computation and so more gas. The base-fee part does not go to validators; it is destroyed (burned), a rule introduced with the London upgrade (EIP-1559) in August 2021.
The fee moves because block space is limited. Each block can hold a set amount of gas, and the base fee rises or falls by up to 12.5% per block depending on whether the previous block was fuller or emptier than the target (half the limit). When transfers pile up, during a popular token launch, an airdrop or a crash, fees can multiply within minutes. If the actual fee is below the maximum fee you set in your wallet, the difference is refunded. Set the tip too low and you wait longer to be included; run out of gas during execution and the transaction fails, yet the gas spent is still charged. Failed transactions cost money too.
Other chains work a little differently. Bitcoin charges by transaction size rather than gas, in satoshis per virtual byte (sat/vB). Because size, not value, sets the fee, spending many small coins you received separately makes a bigger transaction and a higher fee, and when blocks are full, the highest-paying transactions go first. Tron covers fees with energy and bandwidth obtained by staking TRX, or burns TRX when those run short. Layer-2 networks on top of Ethereum (Arbitrum, Optimism, Base and others) bundle transactions and record them on Ethereum, so their fees are far lower, and they fell further after the Dencun upgrade of March 2024. Fee structures and levels differ by chain and change all the time.
Gas is paid in the chain's own coin: ETH on Ethereum, BNB on BNB Smart Chain, TRX on Tron, SOL on Solana. So a personal wallet holding only USDT on the Ethereum network, with no ETH at all, cannot send that USDT. People often move just a token from an exchange to their wallet and then find themselves stuck with nothing to pay gas with. When you send from your own wallet back to an exchange, you pay the gas yourself, so make sure a little of the base coin is there first.
When you withdraw from an exchange, you do not set the gas. The exchange broadcasts the transfer and pays the gas, and charges you a withdrawal fee fixed per coin and per network. Being a fixed amount, it does not track every swing in gas, but when network costs rise or fall for a sustained period, exchanges revise it; in May 2024, Upbit changed the withdrawal fees of 144 coins at once, citing changes in network costs. The same USDT often costs more to withdraw on the Ethereum network than on other networks, and that is the Ethereum gas showing through. Fees change, so check the withdrawal screen each time.
In kimchi premium arbitrage, gas enters the costs in the form of withdrawal fees. With a premium of 1% to 2%, moving a small amount over an expensive network can eat almost all of it, which is why many people look for cheaper networks. The receiving exchange has to support that network and have deposits open, though. And a congested network does not only cost more; it also slows transfers, and the premium can change while you wait.
CoinGaja's Kimchi Premium Calculator takes trading fees, withdrawal fees and order-book slippage off and shows what is actually left, so by trying different amounts you can see how much a fixed withdrawal fee changes the result. Price moves and delays during the transfer are not included. When an exchange suspends deposits or withdrawals for a network upgrade or congestion, the deposit and withdrawal suspension page shows it, and notices such as withdrawal-fee changes appear in Exchange notices.
Example
Plain ETH transfer: 21,000 gas at a base fee of 10 gwei + a tip of 2 gwei → 21,000 × 12 = 252,000 gwei = 0.000252 ETH
With ETH at ₩5,000,000 (about $3,570) → 0.000252 × 5,000,000 = ₩1,260 (about $0.90)
A token transfer assumed to use 65,000 gas (it varies by token) → 65,000 × 12 = 780,000 gwei = 0.00078 ETH → ₩3,900 (about $2.80)
Blocks stay full and the base fee rises 12.5% for 10 blocks in a row → 10 × 1.125^10 = about 32.47 gwei (10 blocks of 12 seconds, about 2 minutes)
A plain transfer then costs → 21,000 × (32.47 + 2) = 723,870 gwei = about 0.000724 ETH → about ₩3,619 (about $2.60)
Moving ₩500,000 (about $357) at a +1.00% premium → expected gain ₩5,000 (about $3.60); lose ₩3,900 to transfer costs and ₩1,100 (about $0.80) is left, before trading fees
※ Example numbers, for illustration only
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