What Is Gas
Paying for computation.
What Is Gas is a free Web3 & DApp Development Fundamentals lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Web3 & DApp Development Fundamentals learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Why Computation Costs Money
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.
What Is Gas?
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.
Gas Units per Operation
Different operations cost different amounts of gas. Simple operations are cheap; storage is expensive.
ADD -> 3 gas
MUL -> 5 gas
SLOAD -> 2100 gas (read storage)
SSTORE -> 20000 gas (new storage)
base tx -> 21000 gasGas vs Gas Price
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.
Gwei: The Fee Unit
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.
1 ETH = 1,000,000,000 gwei
1 gwei = 1,000,000,000 wei
1 wei = smallest unit of ETHCalculating a Fee
The transaction fee is straightforward arithmetic. Multiply the gas your transaction consumes by the price you pay per unit of gas.
gasUsed = 21000
gasPrice = 20 gwei
fee = 21000 * 20 = 420000 gwei
= 0.00042 ETHWhy Gas Exists
Gas serves two purposes:
- Spam prevention — attackers cannot flood the network for free
- Resource pricing — heavy computation costs more, encouraging efficient code
The Halting Problem Solution
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.
while (true) {
// each iteration burns gas
}
// eventually: OUT OF GAS -> revertsWho Receives the Fee?
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.
Gas and Smart Contracts
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.
Putting It Together
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.
Quick Check
Test your understanding of gas.
Recap: What Is 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.
Frequently asked questions
Is the “What Is Gas” lesson free?
Yes — the full text of “What Is Gas” is free to read here on the web, and the Web3 & DApp Development Fundamentals course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Web3 & DApp Development Fundamentals course, upgrade to CoddyKit PRO.
What will I learn in “What Is Gas”?
Paying for computation. You practise Web3 & DApp Development Fundamentals with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Web3 & DApp Development Fundamentals?
No prior experience is required. Web3 & DApp Development Fundamentals on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “What Is Gas” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Web3 & DApp Development Fundamentals lesson?
Yes. Every Web3 & DApp Development Fundamentals lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.