Liquidity Pools and Impermanent Loss, Explained in Plain Language

A liquidity pool is a smart contract holding tokens that people can swap without matching each buyer with a particular seller. The people who deposit tokens are called liquidity providers, or LPs. In return, they may receive a share of the pool’s trading fees and a record of their claim on the pool. But the amounts they can withdraw change as traders swap tokens. If the market price moves, an LP can end up with less value than if they had simply held the same tokens. That difference is called impermanent loss.

What a liquidity provider deposits

In a common pool design, an LP deposits two assets in a specified value ratio. For example, a pool might hold ETH and a dollar-pegged token such as USDC. If ETH is worth $2,000, a deposit of one ETH and 2,000 USDC begins with equal dollar values of the two assets.

The LP is not usually choosing individual buyers or setting a personal asking price. The tokens go into a smart contract, where the pool’s rules make them available for swaps. A trader might send USDC into the contract and receive ETH from it, or do the reverse. The contract updates the amounts it holds according to its design.

Depositors generally receive a claim representing their portion of the pool. Depending on the protocol, that claim might be a fungible pool token or a record of a position with particular settings. The claim is not the same thing as keeping the original tokens untouched in a personal wallet: the LP’s share is tied to the pool’s changing assets and to the contract’s rules.

How swaps change the pool ratio

Consider a simplified constant-product pool containing 10 ETH and 20,000 USDC. Its reserves begin in a 1 ETH to 2,000 USDC ratio, matching an ETH price of $2,000. In this type of pool, a simplified version of the rule is that the two reserve amounts multiplied together stay roughly constant during a swap. The actual amount a trader receives is affected by the fee and the price impact of the trade.

If a trader buys ETH with USDC, USDC enters the pool and ETH leaves. The pool now has relatively more USDC and less ETH. Its quoted price shifts: each remaining ETH costs more USDC. A trade in the opposite direction shifts the ratio the other way. Larger trades relative to the pool’s size generally move the ratio more, which is why a swap can have price impact.

The pool does not necessarily know the wider market price by itself. If its token ratio implies a price that differs from prices elsewhere, traders or automated systems may buy the cheaper asset from the pool or sell the more expensive one into it. Those transactions tend to move the pool’s ratio toward the outside price. This process is often described as arbitrage. It is one reason an LP’s token mix changes when market prices move.

A simple impermanent-loss example

Suppose the pool above has one LP who owns 10% of its liquidity. For simplicity, assume the LP deposited 1 ETH and 2,000 USDC, there are no fees, and no other changes to the pool. At the start, the deposit is worth $4,000: $2,000 in ETH and $2,000 in USDC.

Now suppose ETH’s market price rises from $2,000 to $4,000. Traders can buy ETH from the pool while its price is below the wider market price. In the simplified constant-product model, the pool’s reserves shift toward more USDC and less ETH. After the ratio adjusts, the pool holds about 7.07 ETH and 28,284 USDC. The LP’s 10% share is about 0.707 ETH and 2,828 USDC.

At the new $4,000 ETH price, that share is worth about $5,656: roughly $2,828 of ETH and $2,828 of USDC. If the LP had instead kept the original 1 ETH and 2,000 USDC, those assets would now be worth $6,000. In this example, the pool position is about $344, or 5.7%, lower in value than holding the original assets. That relative shortfall is impermanent loss, before fees.

The example uses rounded figures and a simplified pool, but it shows the central mechanism: as ETH rises, the pool sells some ETH to traders and the LP’s share ends up holding less of the rising asset. If ETH fell relative to USDC, the pool would generally shift toward more ETH and less USDC, compared with the starting mix. The same kind of relative shortfall can occur in either direction when the relative prices diverge.

Why the loss is called impermanent

The term refers to a comparison, not a promise that the shortfall will disappear. If the relative prices return to their starting relationship, the pool’s asset mix may move back toward its initial ratio, reducing or removing this particular difference from holding. But prices may not return. If an LP withdraws while the difference exists, the comparison is no longer just theoretical: the LP receives the assets then available for their share, and the relative shortfall is realized against the hold benchmark.

Impermanent loss also does not always mean the LP has fewer dollars than before. In the example, the position grew from $4,000 to about $5,656. It still did worse than holding, which grew to $6,000. The term describes performance relative to holding the deposited assets, not necessarily an absolute loss of value.

The size of the effect depends largely on how much the asset prices move relative to each other and on the pool’s design. If both assets move by similar proportions, their relative price may change little. If one rises or falls sharply against the other, the pool may rebalance more substantially. Different pool designs use different rules, so the constant-product example should not be treated as a calculation for every pool.

What trading fees can—and cannot—do

Swaps may generate fees for LPs, which can partly or fully offset impermanent loss over a particular period. Whether they do depends on factors including trading activity, the pool’s fee rules, the LP’s share, and how much prices diverge. Fees are not a guaranteed payment that automatically covers a shortfall.

Fee arrangements vary. A protocol may distribute fees to LPs, retain a portion, or handle earnings in another way. Fees might accumulate as tokens in the position, be reflected in the pool, or require a separate claim or action. The details matter: a quoted fee rate alone does not establish what an LP will earn over time.

There is a trade-off. A pool with frequent swaps may collect more fees, but trading volume does not guarantee that fee income will exceed the relative cost of changing asset balances. Fees can also be earned in assets whose values change. Any comparison should account for the value and timing of fees, the value of the withdrawal assets, and what holding the original deposit would have been worth.

Other risks of providing liquidity

• Smart-contract risk: The pool relies on software and contract rules. Bugs, exploits, or failures in connected contracts can cause losses. A familiar token or well-used pool does not remove this risk.
• Token and peg risk: A token designed to track a currency can move away from that value. If one pool asset loses value or becomes difficult to redeem, the pool may hold more of it as traders exchange it for the other asset.
• Network and transaction costs: Depositing, managing, or withdrawing a position may involve network fees. Costs can matter particularly for smaller positions or when several transactions are needed.
• Protocol and liquidity risk: Pool rules, available trading liquidity, and the ability to withdraw can differ. A position may be difficult or costly to manage during congestion or market stress.
• Concentrated-liquidity risk: Some designs let LPs provide liquidity only within a chosen price range. This can make capital more focused, but if the pool price moves outside that range, the position may stop earning swap fees and can become concentrated in one asset. The precise mechanics depend on the protocol.

These risks are separate from impermanent loss, though they can interact with it. Fees may be insufficient even when a contract works as intended, and a contract failure can cause losses unrelated to ordinary pool rebalancing.

Liquidity pools are not the same as spot trading or derivatives

In spot trading, a person buys or sells an asset for another asset, typically through an exchange or directly on-chain. In a liquidity pool, the LP supplies assets for other traders’ swaps and accepts that the pool will change the quantities of those assets. A pool position therefore should not be thought of as simply placing two tokens in a wallet and waiting.

DeFi often involves self-custody: a user controls a wallet and authorizes transactions, while a smart contract holds or manages assets under its programmed rules. This differs from leaving assets with a centralized custodian, such as an exchange that controls the account’s assets on the customer’s behalf. The distinction does not make DeFi risk-free; users still face contract, wallet, transaction, and token risks.

A basic liquidity-pool deposit is also different from a derivative such as a futures contract. An LP generally contributes the underlying tokens to a pool rather than taking a leveraged contract position on a price. Some products can add leverage or derivative-like features, but those require separate explanation. Do not assume a pool position has the same payoff or protections as either holding spot assets or trading a derivative.

Questions to understand before depositing

• Which exact tokens and pool design are involved, and how does the pool change its reserve ratio?
• How are fees collected and distributed, and what other costs apply?
• Does the position have a price range or other settings that affect whether it earns fees?
• What would the position be worth under different relative price changes compared with simply holding the deposit?
• What contract, token, wallet, network, and withdrawal risks apply?

Liquidity provision can be understood as supplying inventory to a trading mechanism in exchange for a possible share of fees. The pool’s rules determine how swaps alter that inventory; the resulting balance may perform differently from the original deposit. Fees can help compensate, but they do not erase the mechanism or guarantee a better result.

Risk reminder: Providing liquidity can result in losses, including losses relative to holding the deposited tokens, and fees may not offset them. Smart-contract failures, token depegs, network issues, changing pool rules, and limited withdrawal options can add further risks. This educational article is general information, not individualized financial advice; understand the specific pool and the possibility of losing value before interacting with it.