FUNDAMENTALS OF CRYPTO

Crypto Gas Fees Explained, What They Are, Why They Exist, and How to Reduce Them

If you have ever sent crypto, swapped tokens, or interacted with DeFi, you have paid a gas fee.

Gas fees are one of the most misunderstood parts of crypto. Many people assume they are random, unnecessary, or even a scam. In reality, gas fees are a core mechanism that keeps blockchains secure, functional, and decentralised.

Understanding how gas fees work helps you avoid overpaying, choose the right networks, and transact more efficiently.

What Are Crypto Gas Fees?

A gas fee is the cost paid to process and validate a transaction on a blockchain.

When you send crypto or interact with a smart contract, your transaction must be included in a block. Validators or miners prioritise transactions that pay higher fees, because fees act as an incentive to secure and operate the network.

In simple terms:

Gas fees pay the network to do work
More complex actions cost more gas
Higher demand means higher fees

Gas is usually paid in the blockchain’s native token.
For example:

Why Gas Fees Exist

Gas fees exist for three core reasons:

Network security

Fees reward validators for verifying transactions honestly. Without fees, blockchains would be vulnerable to spam and attacks.

Fair resource allocation

Blockchains have limited block space. Gas fees help decide which transactions get processed first when demand is high.

Spam prevention

Every transaction has a cost. This prevents bad actors from flooding the network with meaningless transactions.

Without gas fees, decentralised networks would not function reliably.

How Gas Fees Are Calculated

Gas fees are not decided randomly. They are calculated based on three main factors.

Transaction complexity

A simple wallet transfer costs less gas than interacting with a smart contract or DeFi protocol.

Network congestion

When many people are transacting at once, users compete for block space. Fees rise during high demand periods.

Gas price selection

On some networks, users can choose how much they are willing to pay. Paying more usually means faster confirmation.

On Ethereum, fees are typically made up of:

A base fee set by the network
An optional priority fee (tip) paid to validators

How to Read a Gas Fee Before You Confirm

Knowing that fees exist does not help much when a wallet is showing you three numbers and waiting. Here is what each one means.

Gas limit is the maximum units of computational work you will pay for. A plain transfer needs a small, fixed amount. A smart contract interaction needs more, and a complex one needs more again. The limit is a ceiling, not a charge: unused gas is not spent.

Gas price is what you pay per unit, quoted on Ethereum in gwei. One gwei is one billionth of an ETH. This is the number that moves with congestion, and it is the number you are really choosing when a wallet offers you slow, normal, and fast.

Total fee is gas limit multiplied by gas price, shown in the network token and usually converted to a local currency estimate.

Two things regularly confuse people here. First, the estimate can change between opening the wallet and pressing confirm, because the network state moves underneath you. Second, a higher fee does not make a transaction more likely to succeed. It makes it more likely to be included sooner. A transaction that was going to revert will revert faster, and cost more doing it.

Before confirming anything large, check current network conditions on a gas tracker or a blockchain explorer. On Ethereum you can also see what is queued in the pending transaction pool, which is the clearest signal of whether you are about to pay a congestion premium.

Why Gas Fees Fluctuate So Much

Gas fees fluctuate because blockchains operate in real time and have limited capacity.

Every block can only include a certain number of transactions. When demand for block space increases, users compete by paying higher fees to get their transactions processed faster.

Common causes of sudden fee spikes include:

NFT mints that attract thousands of users at once
Major market moves that trigger mass buying, selling, or liquidations
Popular DeFi launches, upgrades, or incentive programs
Airdrops that cause users to rush to claim tokens
Network disruptions or congestion due to technical issues

Because transactions are prioritised by fee size, users who are willing to pay more are processed first. This auction-like system is why fees can rise sharply during peak activity and fall quickly when demand eases.

On networks like Ethereum, this effect is more visible due to consistent high usage. When activity slows, fees naturally drop without any manual intervention.

Failed Transactions Still Cost Gas

This one catches almost everybody once, and it feels deeply unfair the first time.

If a transaction fails, you still pay. The gas fee compensates validators for the computational work of attempting the transaction, and that work happens whether or not the transaction succeeds. A failed swap is not free; it is a swap you paid for and did not get.

Common reasons a transaction fails after you have already paid:

Out of gas. The gas limit you set was too low for what the transaction actually needed. The network does the work up to the limit, runs out, and reverts.
Slippage exceeded. The price moved beyond your tolerance between submitting and executing, so the slippage setting cancelled the trade to protect you.
Missing token approval. The contract was never given permission to move that token, so the transfer step reverts. See token approvals.
The contract rejected it. A condition inside the smart contract was not met.

The practical defence is to stop treating the confirmation screen as a formality. Check the token approval exists, set a slippage tolerance that suits how volatile the asset is, and let the wallet estimate the gas limit rather than trimming it manually to save a few cents. Retrying a failed transaction three times costs three fees.

Which Blockchains Have the Highest and Lowest Gas Fees

Gas fees vary significantly depending on the design and usage of each blockchain.

Higher gas fee networks

Ethereum mainnet generally has the highest fees due to heavy usage and strong decentralisation
Bitcoin fees can spike during periods of congestion, especially when block space demand increases
Older Layer 1 chains with limited throughput may also experience higher costs during peak activity

Lower gas fee networks

Ethereum Layer 2 networks such as Arbitrum, Optimism, and Base offer much lower fees by processing transactions off-chain and settling them on Ethereum
High-throughput Layer 1 blockchains like Solana, Avalanche, and Near are designed for low-cost, high-speed transactions
Newer chains often prioritise scalability, resulting in minimal fees for everyday use

Lower fees do not automatically mean a better blockchain. Trade-offs often exist between cost, decentralisation, security, and network maturity.

Choosing the right network depends on what you are doing, how much value you are transacting, and how important security and decentralisation are for that activity.

What Gas Actually Costs in Practice

By complexity, cheapest to most expensive: sending a native token like ETH is the cheapest action on a network. Sending an ERC-20 token costs more, because it runs contract code. A token approval costs more again. A swap on a decentralised exchange is typically several times the cost of a simple transfer. Minting, bridging, and multi-step DeFi transactions sit at the top.

By network, the gap is far larger than most people expect. The same swap that costs a meaningful amount on Ethereum mainnet during busy periods will often cost a small fraction of a cent on an Ethereum Layer 2 or a high-throughput Layer 1.

That difference is what makes the fee worth thinking about before you act rather than after. A fee that is trivial on a five-figure transfer can be most of the value of a small one. If you are moving $50 AUD, the network you choose matters more than almost anything else about the transaction. See our guide on avoiding high gas fees when trading.

How to Reduce Crypto Gas Fees

There are several practical ways to reduce gas costs.

Transact during low activity periods

Fees are often cheaper during off-peak hours and weekends.

Use Layer 2 networks

Ethereum Layer 2s significantly reduce fees while keeping strong security.

Adjust gas settings manually

Advanced users can lower priority fees when speed is not important.

Batch transactions where possible

Some wallets and protocols allow multiple actions in a single transaction.

Choose the right blockchain for the task

Not every transaction needs to be done on Ethereum mainnet.

Exchange Withdrawal Fees Are Not Gas Fees

These get conflated constantly, and the confusion costs Australian investors money.

A gas fee is paid to the network. An exchange withdrawal fee is charged by the exchange. They are separate, and they are not always related to each other.

When you withdraw crypto from a centralised exchange, the exchange broadcasts the on-chain transaction and pays the actual gas. It then charges you a withdrawal fee, which is often a flat amount per asset rather than the live network cost. That flat fee can be well above what the transaction actually cost the exchange when the network is quiet, and occasionally below it when the network is congested. Some exchanges also batch withdrawals, paying one network fee across many customers while charging each of them individually.

What follows from that is worth acting on. Withdrawal fees differ substantially between Australian exchanges and between assets on the same exchange. Where an asset exists on several networks, choosing the cheaper network at withdrawal time can cut the cost dramatically, provided the destination wallet supports it. And consolidating a few small withdrawals into one larger one avoids paying a flat fee repeatedly.

Our guides on the hidden costs of crypto and withdrawing safely from an exchange cover this in more detail.

Are Gas Fees Tax Deductible?

In many jurisdictions, gas fees may form part of the cost base of a transaction. This depends on how the transaction is classified and local tax rules.

Gas fees should always be recorded accurately, especially when trading, swapping, or interacting with DeFi.

For Australians, gas fees are typically relevant when calculating capital gains or losses. Always keep detailed records and consult official tax guidance or a qualified professional.

For more details on calculating capital gains or losses in Australia, check out our “Capital Gains Tax for Cryptocurrency in Australia” educational resource.

Final Thoughts

Gas fees often get framed as a problem. In reality, they are the compromise that removes the need for middlemen entirely.

Instead of paying a bank, payment processor, or platform to move your money and take a cut, you pay the network directly to settle the transaction. There is no third party deciding whether your transfer is allowed, delayed, or reversed.

That matters.

A gas fee is transparent, predictable, and tied to real network demand. You know what you are paying and why you are paying it. In many cases, paying a few cents or even a few dollars in gas to prioritise a transaction is still cheaper and faster than relying on external processors that charge percentage-based fees, add settlement delays, or impose restrictions.

Gas fees also give users control. If speed matters, you can pay more. If it does not, you can wait and pay less. That flexibility does not exist in traditional systems where fees are fixed and dictated by intermediaries.

Seen this way, gas fees are not friction. They are the middle ground that enables decentralised systems to function without giving up control to a gatekeeper.

Once you understand that trade-off, gas fees stop feeling like a tax and start looking like the cost of financial autonomy.

Frequently Asked Questions

What are gas fees in crypto?

Gas fees are transaction costs paid by users to compensate the validators or miners who process and verify transactions on a blockchain. They are most commonly associated with Ethereum, where every operation from sending tokens to executing smart contracts requires a fee paid in the network's native currency. Gas fees serve two purposes: they prevent spam by making each transaction have a real cost, and they reward network participants for providing the computing resources that keep the blockchain running.

Why do gas fees fluctuate?

Gas fees fluctuate based on network demand. When many users are competing to have their transactions processed at the same time, they bid up the price of gas to get priority inclusion in the next block. During periods of high activity, such as a popular NFT launch, a DeFi protocol collapse, or a sharp market move, gas fees on Ethereum can spike dramatically. During quieter periods, fees fall to more moderate levels.

How are Ethereum gas fees calculated?

Ethereum gas fees are calculated by multiplying the gas units consumed by a transaction by the current gas price in Gwei, which is a small denomination of ETH. Since the EIP-1559 upgrade in 2021, fees are split into a base fee, which is burned and removes ETH from circulation, and a priority tip paid directly to the validator who includes the transaction. The base fee adjusts automatically based on how full the previous block was relative to target capacity.

How can you reduce gas fees on Ethereum?

Several strategies can reduce the gas fees you pay. Transacting during off-peak hours, typically weekends or overnight UTC time, when network activity is lower can result in lower base fees. Using Ethereum layer 2 networks such as Arbitrum, Optimism, or Base dramatically reduces fees for most DeFi interactions. Batching multiple operations into a single transaction reduces the per-operation cost. You can also set a lower gas limit in your wallet and wait longer for the transaction to be included.

Are gas fees the same on every blockchain?

No. Gas fees vary significantly across blockchains. Ethereum mainnet has historically charged the highest fees during congestion periods, sometimes exceeding $100 AUD per transaction. Solana charges fractions of a cent per transaction due to its high-throughput architecture. BNB Smart Chain and Polygon also offer much lower fees than Ethereum mainnet. The trade-off is often between fee cost and the level of decentralisation and security the network provides.

What was EIP-1559 and how did it change gas fees?

EIP-1559 was a major Ethereum upgrade implemented in August 2021 that fundamentally changed how gas fees work. Before EIP-1559, users bid gas prices in a simple auction where miners collected all fees. After EIP-1559, a base fee is algorithmically set for each block and burned, reducing ETH supply. Users add a small priority tip to incentivise faster inclusion. The change made fee estimation more predictable and introduced a deflationary pressure on ETH supply through fee burning.

Do you lose gas fees if a transaction fails?

Yes. Gas fees compensate validators for computational work, and that work is performed regardless of whether the transaction succeeds or fails. If a smart contract interaction fails due to insufficient gas, slippage, or a contract error, the gas consumed up to the point of failure is still charged. This is why it is important to set appropriate gas limits and verify transaction parameters before confirming, particularly for complex DeFi interactions.

Are gas fees tax-deductible in Australia?

The Australian Taxation Office has indicated that transaction costs including gas fees may form part of the cost base of a crypto asset when determining capital gains. This means gas fees paid when acquiring an asset can increase its cost base, potentially reducing your capital gain when you dispose of it. Gas fees paid on transactions that generate income may also be deductible against that income in some circumstances. Given the complexity, consulting a tax professional with crypto expertise is strongly recommended.

WRITTEN & REVIEWED BY Chris Shepley

UPDATED: AUGUST 2026