Impermanent Loss: The Hidden Cost
The previous lesson ended with a deliberately incomplete number: a fee-only yield estimate for providing liquidity. This lesson explains the cost that estimate was missing — impermanent loss (IL), the single most important concept for anyone considering liquidity provision, and the reason "high APR" pools can still lose money in dollar terms.
Recall that as an LP, you own a percentage share of a pool, not a fixed quantity of each token. As the price of the two tokens in the pool shifts relative to each other, the AMM's constant-product formula automatically rebalances the pool's internal ratio — effectively, arbitrageurs trading against the pool sell the token that's become relatively more valuable and buy the one that's become relatively less valuable, in order to bring the pool's implied price back in line with the broader market. This means that if one of your two deposited tokens rises sharply in price, the pool has already automatically sold some of it into the other token by the time you withdraw — so you end up with less of the appreciating asset than if you had simply held both tokens separately without depositing them.
The loss is called "impermanent" because, in theory, if prices return exactly to where they were when you deposited, the effect fully reverses and there's no loss at all. But if you withdraw while prices are still diverged from your entry point, that loss becomes real and permanent at the moment of withdrawal — "impermanent" is a description of a theoretical possibility, not a promise. This is precisely why comparing your fee income against your potential IL, which the next lesson teaches you to do directly, is the central judgment call of liquidity provision.
Worked Example
Suppose you deposit $500 of ETH and $500 of USDC into a pool when ETH is trading at $2,000 (so your $500 buys exactly 0.25 ETH, paired with $500 USDC). If ETH then doubles to $4,000, and you had simply held your original 0.25 ETH and $500 USDC outside any pool, your holdings would now be worth $1,000 (0.25 ETH × $4,000) + $500 USDC = $1,500 total.
But because you deposited into an AMM pool, the pool's constant-product formula automatically sold some of your ETH into USDC along the way as arbitrageurs traded against it to keep the pool's price aligned with the market. Using the standard impermanent loss formula for a 50/50 pool, a 2x price change produces an IL of approximately 5.7% relative to simply holding — meaning your LP position, ignoring trading fees entirely, would be worth approximately $1,414 instead of the $1,500 you'd have from holding, a $86 shortfall purely from the pool's automatic rebalancing. Whether this $86 loss was "worth it" depends entirely on how much you earned in trading fees over the same period — which is exactly the comparison the next lesson, "LP Math," walks you through.
It's also worth being precise about a common misconception: impermanent loss is not something that happens to your deposit through a fee, a penalty, or any action by the protocol — it's purely an opportunity cost that emerges from comparing your actual LP outcome against the hypothetical alternative of simply holding both tokens separately. Your LP position never "loses" money in an absolute sense purely from IL alone (ignoring fees, it can even still be worth more than your original deposit if both tokens rose in price, just less than holding would have been worth). This distinction matters because it changes the right question to ask: not "did I lose money providing liquidity?" but "would I have been better off simply holding?" — and that second question is exactly what comparing fee income against IL, the subject of the next lesson, answers directly.
Common Pitfalls
- Assuming IL only matters for large price moves. Even moderate, realistic moves (1.5x–2x) produce meaningful IL percentages, as the worked example above shows — don't reserve this concern only for extreme volatility.
- Forgetting that IL compounds with correlation. Two tokens that tend to move together (like ETH and a liquid-staked ETH derivative) experience far less IL than two unrelated tokens, a concept the next lesson develops fully.
- Confusing "impermanent" with "irrelevant." The loss only reverses if you don't withdraw while prices are diverged — many LPs withdraw during exactly the price swings that lock in the loss permanently.
Exercise
Using the standard impermanent loss formula — IL = [2 × √(price ratio)] ÷ (1 + price ratio) − 1, where "price ratio" is the new price divided by the original price of one asset relative to the other — or an online impermanent loss calculator if you prefer not to compute it by hand, calculate the impermanent loss percentage for three scenarios: one asset moving to 1.5x its original relative price, moving to 2x, and moving to 4x.
For each of the three scenarios, compare the IL percentage to the fee-only yield estimate you calculated in the previous lesson's exercise, scaled to the same time period if needed. Note at roughly what size of price move your estimated fees stop covering the impermanent loss — this crossover point is exactly the kind of judgment call the next lesson formalizes into a decision framework.
Recap
- Impermanent loss occurs because an AMM pool automatically rebalances your share as prices move, leaving you with less of the appreciating asset than if you'd simply held.
- The loss is "impermanent" only if prices return to your entry point before you withdraw; otherwise it becomes real and permanent at withdrawal.
- Comparing your fee income against your IL at various price-move scenarios tells you whether a specific pool is actually worth providing liquidity to.