You can estimate a V2 pool’s impermanent loss from the change in its token price ratio, then weigh that shortfall against trading fees and any farm rewards. The calculation is most useful for a standard 50/50 pool; other pool designs can behave differently. For the broader choice, see how BaseSwap swaps and pools differ; this guide focuses on one risk to check before supplying liquidity.
What does impermanent loss measure?
Impermanent loss is the difference between the value of your pool position and the value of simply holding the same tokens. It comes from the pool automatically changing the mix of tokens as their relative prices move.
In a V2 pool, the reserves follow a constant product: token A multiplied by token B stays roughly constant as trades shift the balances. Arbitrage traders bring the pool’s price back toward the wider market, so after one token rises, the pool holds less of it and more of the other. That rebalancing creates the shortfall relative to holding.
The loss is “impermanent” because a return to the original price ratio can shrink it; withdrawing while prices remain changed makes the difference real. The calculation compares token quantities at the same current prices, before counting fees or rewards.
How can you estimate it before depositing?
Use the change in the pair’s relative price, not the percentage change of one token in isolation. For a standard 50/50 V2 pool, the estimate is 2 × √r ÷ (1 + r) − 1, where r is the final token A-to-B price ratio divided by its starting ratio.
- Identify the exact pair and pool type. Check that it is a standard V2, equal-value pool. Write down which asset is A and which is B, plus their market prices when you would enter. A different weighting or concentrated range needs a different model.
- Choose a price scenario. Estimate the future price of A in B, then divide that by today’s A-in-B price. If A is currently worth 500 units of B and later 1,000, r = 2. Reversing the token order gives r = 0.5 and the same result.
- Calculate the percentage shortfall. With r = 2, the formula gives about −5.72%. Treat this as an example, not a forecast: it means the pool position would be worth roughly 5.72% less than holding the original token quantities, before fees and rewards.
- Convert the estimate into money. If you deposit $1,000 split equally between the tokens, and one token doubles while the other stays level, the pool position would be about $1,414 while holding would be $1,500. The example shortfall is about $86.
- Compare possible income separately. Estimate your share of trading fees from pool volume and your share of liquidity, then account for any farm rewards separately. Fees vary with actual trades; rewards can change in amount or token value. Neither is guaranteed to offset the shortfall.
When does the estimate change your decision?
Use it to compare outcomes, not to predict a break-even date. A pool with frequent trading may earn more fees, but volume, your share of liquidity and the price path all matter; a liquidity farm adds potential rewards while also exposing you to the reward token’s price. On Base, BaseSwap is one venue where someone can supply liquidity, but the same comparison applies: forecast the pair’s relative price, then assess likely income against the risk.
A common mistake is to see a high advertised reward and treat it as guaranteed compensation for impermanent loss. Instead, calculate a low-reward or zero-reward case and ask whether you would still accept the resulting token mix if the price ratio moved against you. Also check that both tokens are the assets you intend to hold; a pool can leave you heavily weighted toward the weaker performer.
In short, model the pair’s relative price move first, use the V2 formula as a baseline, and add fees or farm rewards only as uncertain income. The key decision is whether the possible shortfall and changed token mix fit your plan.