Gas is the fee paid to process a transaction or run a smart contract on Ethereum, priced in gwei and paid in ETH. One gwei is a billionth of an ETH. It matters to buyers because moving ETH, or Ethereum tokens such as USDT or USDC, later costs gas, so the wallet needs a little ETH.
How is gas calculated?
A gas fee is the gas units used, multiplied by the base fee plus a tip. It is Ethereum’s network fee, paid for the computing work of an ETH transfer or a smart contract.
- Base fee: set by the network for each block and burned since the London upgrade (August 2021, EIP-1559).
- Priority fee: a tip to the validator who includes your transaction.
- Gas limit: the most gas units you allow. Unused gas is refunded.
What is an example of a gas fee?
A simple ETH transfer uses 21,000 gas units. With ethereum.org’s example figures of a 10 gwei base fee and a 2 gwei tip, it costs 21,000 × 12 = 252,000 gwei, or 0.000252 ETH. Real prices change every block, so check a live tracker such as Etherscan’s gas tracker, and use the Ethereum calculator to convert ETH into your currency.
Why do gas prices change?
Gas prices follow demand for block space. The base fee moves up or down by at most 12.5% per block, and in busy periods users raise their tips to get ahead in the mempool. Layer 2 rollups bundle many transactions into one on Ethereum so users share the cost, and the Dencun upgrade (March 2024) cut their data costs (ethereum.org, as of September 2026).
Why do gas fees matter when you buy crypto?
You pay gas in ETH whenever you later move ETH or ERC-20 tokens such as USDT or USDC on Ethereum, so keep a little ETH in that wallet. Crypto is delivered to the wallet address you provide. Coinmama does not add its own fee. All fees are shown before you confirm your order. See what you pay when you buy crypto on Coinmama, or see the Ethereum price and payment options.
What are the risks and red flags?
- Failed transactions still cost gas: if a transaction fails or runs out of gas, the gas it used is not returned.
- No ETH, no transfer: a wallet holding only tokens cannot send them.
- Fake fee demands: scams often say you must pay a fee to withdraw your money (FTC). Real gas comes from your own wallet when you send. See how to protect yourself from fraud.
Go deeper: What is Ethereum?
