What are gas fees, and why does using crypto cost money?

Every time you send Bitcoin, mint an NFT or swap one token for another, you pay a small fee that has nothing to do with the price of the asset itself. That fee is what the crypto world calls a gas fee, and it is one of the most misunderstood costs in the whole ecosystem. People expect digital money to be free in the way that sending an email is free, then they discover that moving fifty pounds of Ethereum across town costs them three pounds in fees, and the obvious question is why.

The short answer is that someone has to do the work, and someone has to be paid for it. Blockchains are not run by a single company sitting in a data centre. They are run by thousands of independent computers around the world, all racing to confirm transactions, agree on a shared record, and keep the network honest. Those computers consume electricity, hardware and human attention. The gas fee is the price you pay them for processing your transaction and adding it to the permanent ledger.

The word gas is a useful metaphor, even if it sounds odd at first. Think of the blockchain as a motorway and your transaction as a car. Different journeys require different amounts of fuel. A simple transfer of a few coins from one wallet to another is a short trip in a small car. A complex DeFi transaction that swaps tokens, locks them in a lending pool, and updates several smart contracts at once is more like driving a removal lorry across the country. The fee reflects how much computational work the network has to do to complete the journey.

On Ethereum, gas is measured in tiny units called gwei. Each operation that the network performs has a fixed gas cost, set by the protocol. Sending ether to another wallet costs around 21,000 units of gas. Interacting with a smart contract might cost ten or twenty times that amount. The total fee you pay is the gas units multiplied by the current gas price, which moves up and down depending on how busy the network is. When everyone wants to use Ethereum at the same time, perhaps because a popular NFT is launching or a major airdrop is happening, the gas price spikes and ordinary transactions can suddenly become expensive.

This is the part that frustrates people most. The fee is not fixed by your bank or by an exchange. It is set by an open auction. Validators on the network choose which transactions to confirm next, and they tend to pick the ones offering the highest fee. If you are willing to pay more, your transaction goes through quickly. If you set the fee too low, your transaction sits in a queue called the mempool, sometimes for hours, sometimes never confirming at all. During the worst congestion of the 2021 NFT boom, simple Ethereum transactions cost over a hundred pounds. That was not a glitch. It was the auction working exactly as designed.

Different blockchains handle this very differently. Bitcoin charges fees too, but the system is simpler because the only operations are sending coins from one address to another. Bitcoin fees rise during congestion in much the same way as Ethereum, though they tend to be lower for everyday transfers. Solana takes a completely different approach. Its network is engineered to process thousands of transactions per second, and fees are usually a fraction of a penny regardless of how busy things are. The trade off is that Solana has had several network outages over the years, which Bitcoin and Ethereum have not.

Layer 2 networks were built to solve the gas fee problem on Ethereum without abandoning Ethereum altogether. Networks like Arbitrum, Optimism and Base bundle hundreds of transactions together off the main chain, then post a single compressed proof back to Ethereum. The result is that users on these networks pay pennies instead of pounds, while still benefiting from Ethereum’s underlying security. For most everyday DeFi activity, layer 2 networks are now the default choice for anyone who does not want to be priced out by gas costs.

It is worth understanding what you are actually paying for, because the gas fee is not arbitrary. It is the only mechanism that protects the network from spam. If transactions were free, anyone could flood the blockchain with millions of pointless requests and bring it to a halt. The fee creates a real economic cost for using the network, which means only transactions worth doing actually get done. That is the same logic behind charging postage on letters or fares on trains. It is not the company being greedy, it is the system filtering out abuse.

Gas fees are also how the network pays the people securing it. On Ethereum, validators stake their own ether to participate, and they earn fees from every transaction they confirm. On Bitcoin, miners receive fees alongside the block reward for the energy they spend on proof of work. Without fees, there would be no incentive for anyone to keep the network running, and the whole thing would collapse. The fee is the economic glue that holds decentralised systems together.

For UK readers using crypto in practice, the lesson is to plan around gas costs rather than be surprised by them. Avoid sending small amounts of Ethereum directly on the main chain when fees are high. If you are doing DeFi or trading regularly, learn to use a layer 2 network. Most reputable wallets like MetaMask now show you the estimated gas fee in pounds before you confirm a transaction, and many give you the option to pay slow, average or fast. There is no shame in choosing slow if you are not in a rush. Tools like Etherscan’s gas tracker show you the current network conditions and help you time transactions for cheaper periods, often late at night UK time when the US is asleep.

The bigger picture is that gas fees are not a flaw in crypto. They are the price of running a financial system that no single company controls. Visa and Mastercard charge merchants two or three percent on every transaction, but you never see it because the cost is buried in the price of what you buy. Crypto puts the cost in front of you, in real time, in your own wallet. That can feel jarring at first, but it is also more honest. You are paying for the network, and the network is paying you back in the form of independence from the institutions that would otherwise be in the middle of your money.

Disclaimer: Cryptocurrency investments are highly volatile and speculative. Their value can rise and fall sharply, and you could lose all of your investment. This article is for informational and educational purposes only and does not constitute financial advice. Always do your own research before making any investment decision.