Impermanent loss is the value gap between holding tokens and keeping them in a liquidity pool as prices change. It matters when you provide liquidity on Base because the pool automatically adjusts its token mix as traders buy and sell.
If you need the broader mechanics of using BaseSwap for swaps and pools, that guide covers them; here, the focus is the risk a pool provider takes. The key comparison is your pool share against simply holding the same tokens, measured at the same market prices and time.
Why does a pool change what you hold?
A pool’s pricing rules change its token balances as trades move the price. In a classic 50/50 constant-product pool, the reserves follow the rule x × y = k: as the amount of one token falls, the amount of the other rises so their product stays constant, before accounting for fees.
When one token becomes more valuable, traders tend to buy it from the pool and add the other token. Arbitrage traders—who trade against price differences across markets—help bring the pool’s price back in line. Your share of the pool is then worth a different combination of tokens than the one you deposited.
That automatic rebalancing is the source of impermanent loss. It is not a separate charge, and tokens have not vanished; the pool has shifted your exposure toward the token that fell in relative value.
What does impermanent loss look like in an example?
Suppose you deposit 1 ETH and 2,000 USDC when each side is worth $2,000. If ETH’s market price doubles to $4,000, a classic constant-product pool would hold about 0.707 ETH and 2,828 USDC for your share, assuming no fees or other liquidity changes.
At the new prices, that position is worth about $5,657. If you had held the original 1 ETH and 2,000 USDC instead, they would be worth $6,000. The pool position is therefore about $343, or 5.7%, behind holding.
The calculation compares like with like: the same starting assets, the same ending prices, and no trading fees. For a simple 50/50 constant-product pool, the relative change in price drives the gap; a doubling or halving produces roughly the same percentage loss against holding. The larger the price move, the larger the gap tends to be.
When is the loss “impermanent”?
It is called impermanent because the gap can shrink if the relative token price returns to where it was when you deposited. In the example, if ETH returns to $2,000, the pool’s token mix may return to its starting ratio, before fees and other changes.
But the name can mislead: the loss becomes real relative to holding if you withdraw while prices remain changed. A position can also finish with a different result if you add or remove liquidity, collect fees, or prices move along a more complicated path. Check the position’s current value against the value of the tokens you would have held; don’t assume a later recovery.
Pool design matters, too. The example describes a full-range, constant-product pool. A pool with concentrated liquidity, where providers choose a price range, can behave differently: once the market price moves outside your range, your position may hold only one token and stop earning trading fees until the price returns or you adjust it.
How should you decide whether fees justify the trade-off?
Compare expected fee income with the loss you could face at plausible price changes, then include the cost of entering and exiting. Fees depend on actual trading volume and your share of active liquidity; they are variable, not a promised yield. Network transactions on Base also use ETH for gas.
A common mistake is choosing a pool because its displayed fee rate or recent returns look high. A high rate alone says little about how much trading occurs or how much liquidity competes for those fees. Look at the pair’s price relationship, the pool’s activity, and whether you would be comfortable holding either token if the market moves sharply.
BaseSwap can be a route to provide liquidity on Base, but the pool’s economics determine whether the position suits you. Before adding liquidity through BaseSwap, decide what price movement you can tolerate and compare the position’s likely fees with the value you would give up by not holding the tokens.
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