Gas fees on Ethereum: Understanding their fluctuations

Gas fees are the part of using Ethereum, and blockchains built on similar models, that trips up newcomers the most: the same action can cost a few cents or several dollars depending on when it’s submitted, for reasons that aren’t obvious from the wallet interface alone.

Gas measures work, not value

Every action on Ethereum, sending ETH, swapping a token, minting an NFT, interacting with a smart contract, requires the network’s computers to actually execute that code. Gas is the unit that measures how much computational work an action requires: a simple ETH transfer costs a fixed, small amount of gas, while a complex smart contract interaction, several steps executed in sequence, costs more. The gas fee is the amount actually paid, calculated as the gas used multiplied by the gas price at the time, and paid in ETH regardless of what token or asset the transaction involves.

Why the price of gas moves

Block space on Ethereum is limited: each block can only include so much total gas. When more people want their transactions processed than the network can fit into the next block, they effectively bid against each other, offering to pay more per unit of gas to get priority inclusion. That’s why gas fees spike during periods of high demand, a popular NFT mint, a volatile market moving fast, a widely used application launching, and fall back down during quieter periods when fewer transactions are competing for the same block space.

This is fundamentally an auction dynamic, and it behaves the way auctions generally do: demand spikes are self-reinforcing in the short term, because a transaction offering too low a fee simply doesn’t get included in the next block and instead waits, competing again against a fresh wave of new transactions in the following block, which keeps upward pressure on fees until enough of the initial surge in demand clears. A transaction stuck with too low a fee during a busy period isn’t rejected outright; it typically sits pending until either network conditions ease or the sender manually increases the fee to jump ahead of the backlog.

Why gas is priced separately from what you’re sending

A common point of confusion for newcomers is that a transaction’s gas fee is unrelated to how much value is being transferred. Sending $10 worth of ETH and sending $10,000 worth of ETH cost exactly the same amount of gas, because gas measures computational work, not dollar value. This is different from how fees work in traditional finance, where a wire transfer fee or a brokerage commission is sometimes calculated as a percentage of the amount moved. On Ethereum, the cost is tied entirely to what the transaction asks the network to compute: a basic transfer requires a small, fixed unit of work regardless of size, while a multi-step interaction with a decentralized exchange or lending protocol requires more computation and therefore costs more gas, even if the dollar amount involved is small. That distinction matters practically for anyone moving small amounts: a $20 transfer during a period of high network congestion can cost a meaningful percentage of the amount being sent in gas fees alone, which is one of the more common frustrations newcomers run into.

How EIP-1559 changed the mechanism

Ethereum’s London upgrade, implemented in August 2021 through a change called EIP-1559, restructured how fees work. Instead of a single bid-style gas price, each transaction now pays a base fee, which is set algorithmically based on how full recent blocks have been and is burned, permanently removed from circulation, rather than paid to anyone. On top of that, users can add a priority fee, a tip paid directly to the validator that includes the transaction, to jump the queue during busy periods. The base fee adjusts up or down by a bounded amount block to block, which makes near-term fees more predictable than the old auction system, though it doesn’t cap what fees can reach during a sustained surge in demand.

What actually affects a fee day to day

Three things determine what a transaction costs: how much gas the action itself requires, how congested the network is at that moment, and how much priority fee is offered. Wallets typically suggest a gas price automatically based on current network conditions, and most let a user check network congestion before submitting, or simply wait for a quieter period, since gas prices on Ethereum can vary by a large multiple between a busy afternoon and an off-peak overnight window. Layer-2 networks built on top of Ethereum, and other blockchains with different designs entirely, exist partly as a response to this cost structure, processing transactions more cheaply and settling back to Ethereum’s base layer periodically.

How Layer-2 networks change the math

A Layer-2 network, such as a rollup, processes transactions on its own, separate infrastructure and then periodically bundles and submits a compressed summary of that activity back to Ethereum’s base layer, referred to as Layer 1. Because the Layer-2 network is handling the bulk of individual transactions itself rather than submitting each one directly to Ethereum, users pay gas fees denominated in the Layer-2’s own, typically far cheaper, fee structure for most of their activity, with only the periodic batch settlement incurring Ethereum’s base-layer costs, spread across potentially thousands of bundled transactions rather than paid individually. The tradeoff for that lower cost is usually a modest difference in security assumptions or withdrawal times, since moving assets back from a Layer-2 to Ethereum’s base layer can, depending on the specific rollup design, take anywhere from minutes to about a week to fully finalize, a detail worth checking before assuming funds can move between layers instantly.

What other blockchains do differently

Not every blockchain uses Ethereum’s fee-market model at all. Some networks use a different consensus and fee design specifically to avoid Ethereum-style congestion pricing, charging flat, low fees regardless of network demand, though usually by making different tradeoffs elsewhere, such as a smaller or more centralized validator set, or different assumptions about how the network handles a sudden surge in demand. Understanding that gas fees, and the way they spike, are a specific design choice tied to Ethereum’s particular fee-market mechanism, rather than an unavoidable feature of blockchains generally, is useful context for anyone comparing the cost of using different networks for the same basic action.