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Every operation on Ethereum runs on thousands of nodes worldwide. To prevent abuse and pay for this work, the network charges gas.

Gas is the unit that measures computational effort.

Gas is a unit of measurement for the work required to execute operations on the EVM.

Sending ETH, calling a contract, or storing data each consume a specific amount of gas based on their complexity.

Different operations cost different amounts of gas. Simple operations are cheap; storage is expensive.

Keep two ideas separate:

• Gas used — how much computation the transaction needs (units)
• Gas price — how much you pay per unit, measured in gwei

Total fee = gas used multiplied by gas price.

Gas prices are quoted in gwei, a tiny fraction of ETH. One gwei equals one billionth of an ETH (10^-9).

Quoting in gwei keeps numbers readable instead of writing many leading zeros.

The transaction fee is straightforward arithmetic. Multiply the gas your transaction consumes by the price you pay per unit of gas.

Gas serves two purposes:

• Spam prevention — attackers cannot flood the network for free
• Resource pricing — heavy computation costs more, encouraging efficient code

Gas also stops infinite loops. Each step consumes gas, and when a transaction runs out, execution halts.

This guarantees the EVM always terminates — you cannot freeze the network with a runaway loop.

Gas fees compensate the validators who include and execute your transaction.

Under EIP-1559, part of the fee is actually burned (destroyed), and a smaller tip goes to the validator. We cover this in a later lesson.

Complex smart contract calls cost more gas than simple transfers because they execute many operations.

Efficient contract code directly lowers user costs — gas optimization is a core skill for Solidity developers.

Gas measures computational work; gas price (in gwei) sets the cost per unit. Their product is your fee.

Gas prevents spam, prices resources fairly, and guarantees execution always terminates.

Test your understanding of gas.

You learned that:

• Gas measures computational work on the EVM
• Gas price is paid per unit in gwei
• Fee = gas used multiplied by gas price
• Gas prevents spam and stops infinite loops

Next: the full lifecycle of a transaction.