Impermanent loss is the difference between the value of your tokens in a liquidity pool and what those same tokens would be worth if you had simply held them. It happens when their prices move relative to each other after you deposit them; trading fees can offset the difference, but do not guarantee a profit.
Why can a pool be worth less than holding the tokens?
A classic 50/50 automated market maker (AMM) adjusts its token reserves as people trade, following the constant-product rule x × y = k. Here, x and y are the quantities of each token, and k is their product. As the outside market price shifts, arbitrage traders trade against the pool until its price is closer to the market price. The pool ends up holding a different mix of tokens than you deposited.
That change in mix is the mechanism behind impermanent loss. If one token rises relative to the other, the pool sells some of the rising token for the other asset as traders rebalance it. Your share still represents a claim on the pool, but you may own less of the asset that rose than if you had held both tokens untouched.
How large can the difference get?
Consider an illustrative ETH/USDC pool. You deposit 1 ETH at $1,000 and 1,000 USDC, worth $2,000 in total. If ETH then rises to $4,000 while USDC stays near $1, the pool’s reserves rebalance. Ignoring fees, your share would be worth about $4,000, compared with $5,000 if you had held the original 1 ETH and 1,000 USDC.
In this example, the pool position is 20% below the hold value, or $1,000. That is impermanent loss measured against holding, not necessarily a loss compared with your original $2,000 deposit: the pool position has doubled in dollar value. The percentage changes when the relative price move changes. For a classic 50/50 pool, a fourfold rise or fall in one token relative to the other produces about a 20% difference from holding, before fees.
The word “impermanent” describes the comparison, not a promise that the gap will disappear. If relative prices return to where they were when you deposited, the pool’s token mix can return toward its starting ratio. If you withdraw while prices remain changed, the difference is realized in the value of what you receive.
Do fees or liquidity farming cover the difference?
Fees help only when your share of accumulated fees exceeds the pool’s impermanent loss, plus any costs of entering and exiting. Fees depend on the pool’s fee rules, trading volume, your share of liquidity, and—where liquidity is concentrated—whether the market price stays inside your chosen range. Liquidity farming rewards, if offered, are separate incentives; their value can change and should not be treated as guaranteed fee income.
Before adding funds on Base, compare the pool position with the hold alternative and check the pool design. The base swap is a concrete example of the Base network setting where someone may be considering a token swap or liquidity position; the comparison itself applies to AMM pools generally. A classic full-range pool and a concentrated-range position do not have identical exposure: with concentrated liquidity, being outside your range can stop fee earnings until the price returns or you adjust the position.
What should you check before adding liquidity?
Estimate the outcome using these inputs, then decide whether the possible fee income makes the exposure worthwhile for your time horizon:
- The two tokens and their current relative price.
- The price change you want to model, in either direction.
- Whether the pool uses full-range or concentrated liquidity, and any range you must choose.
- Your estimated share of trading fees and any farming rewards, treated separately.
For base swap liquidity decisions, the deciding comparison is your pool share at the price you expect to withdraw against simply holding the deposited tokens. A pool can be profitable in dollar terms and still underperform that alternative; the reverse can also happen if accumulated fees are large enough.
One practical tip: write down the token quantities you deposit and their value at that moment. At review time, compare the value of your withdrawable pool share—including earned fees—with the value of those original quantities at current prices; that makes the trade-off visible before you commit more funds.
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