Balancer is a weighted AMM that shapes LP exposure and impermanent loss

Balancer weighted pools beside Uniswap v3

Balancer weighted pools keep liquidity active across the full price curve, while Uniswap v3 concentrates capital inside ranges selected by liquidity providers.

A standard v3 Weighted Pool holds 2 to 8 tokens, assigns every token at least a 1% weight, and requires normalized weights to total 100%. Allocations such as 80/20 or 60/20/20 let LPs express an index-like mix while every token remains available for swaps. Uniswap v3 instead pairs exactly 2 tokens, and each position earns fees only while the market price stays inside its chosen range. That concentration improves capital efficiency near the active price, but it adds range selection and repositioning work that a full-range weighted pool avoids. Both designs expose LP inventory to price movement.

Curve StableSwap targets tightly correlated assets with a flatter curve near parity. Weighted math instead serves uncorrelated assets such as WETH, WBTC, and USDC in an 80/20 or 60/20/20 portfolio.

Fees, gas, and the LP return equation

More broadly, Balancer costs separate into the pool’s swap fee, the network gas fee, and any price impact created by the selected route or liquidity action.

A standard v3 Weighted Pool accepts a static swap fee from 0.001% through 10%, recorded at 0.00001-percentage-point resolution. The Vault charges that percentage on the input amount for each swap. It also charges the fee on only the non-proportional portion of an unbalanced add or removal. A proportional liquidity action avoids pool-level price impact. Some v3 pools attach a hook that computes a dynamic fee for each swap, so the interface quote matters more than the stored static reference. Weighted Pool contracts express fees as 18-decimal fixed-point values before the Vault packs them for storage.

Displayed yield also moves with trading volume, pool depth, external incentives, and the protocol’s fee share; it isn’t a fixed return.

Gas goes to the network’s validators or sequencer, not to LPs. A route spanning several pools performs more contract work than a direct swap. Price impact grows as an order becomes large relative to the relevant balances, especially on the lighter side of an asymmetric pool. Compare expected fee income with gas, price impact, and inventory rebalancing over the same holding period.

How does the weighted invariant move a pool?

The weighted invariant keeps the product of token balances raised to their normalized weights constant before fees, so trades change balances and therefore spot prices.

For token balances b and normalized weights w, weighted math uses an invariant of the form V = Π b ^w . The weights sum to 1, which is the fixed-point equivalent of 100%. A 50/50 two-token pool reduces to the familiar constant-product shape, while unequal weights tilt the balance requirements. The spot price between two assets comes from their balances after each balance is divided by its weight. Before the pool evaluates a swap, the fee leaves the input amount. Arbitrage then trades against any difference between that on-chain spot price and prices elsewhere.

Once that is set, Balancer v3 separates those calculations from custody. The Vault holds standard ERC-20 tokens and performs accounting, a Router carries the user’s action, and the pool contract returns the mathematical result. This separation lets Weighted Pools, Stable Pools, Gyro pools, and custom pool logic share the same settlement layer without sharing the same pricing curve.

Choosing a pool and adding liquidity

A Balancer entry starts with a supported network, an ERC-20 wallet, and a pool whose token mix, weights, fee mode, and hook configuration match the intended exposure.

Ethereum, Arbitrum, Base, and Gnosis Chain host deployments, with chain IDs 1, 42161, 8453, and 100.

MetaMask and Rabby provide common wallet paths. On v3 retail routes, Permit2 handles input-token authorization: the wallet approves Permit2 once per token, then grants a specific Router an amount-limited, expiring permission. Tokens that implement EIP-2612 support signature-based permits, which compatible calls can bundle with the liquidity action. The wallet also needs the selected network’s native gas token.

Read the transaction preview before signing. A proportional add supplies tokens in the pool’s current ratios and avoids the internal swap effect. Unbalanced and single-token adds are available through supported v3 routes, but their non-proportional portion incurs the pool’s swap fee and price impact. The completed add issues Balancer Pool Tokens (BPT), ERC-20 receipts that represent the wallet’s proportional claim on pool assets.

Impermanent loss under unequal weights

Impermanent loss in a Balancer weighted pool measures the LP position’s value against simply holding the same starting assets after their relative prices change (more on this in Balancer basics ).

Arbitrage keeps the weighted spot price aligned with outside markets by removing some of an appreciating asset and adding more of the other asset. The pool therefore rebalances by selling into strength and buying into weakness. A higher weight on the appreciating token reduces divergence loss for that move relative to a 50/50 pool, although the lighter reserve also creates greater slippage for some trades. Collected fees offset part of the gap only when actual volume supplies enough revenue.

In this hypothetical worked example, the starting position is $10,000, token A has an 80% weight, a stable asset has a 20% weight, token A’s price doubles, and fees, incentives, and gas equal zero. Holding produces $18,000: the original $8,000 token A allocation becomes $16,000, while the stable allocation remains $2,000. The fee-free weighted position becomes $10,000 × 2 ^0.8 , or $17,411.01. Relative to holding, the LP trails by $588.99, which is 3.27% impermanent loss.

Fee income would raise the pool value, so the realized gap differs from this fee-free 3.27% calculation.

When do weighted pools fit the job?

Weighted pools fit portfolios that need continuous rebalancing, persistent full-range liquidity, and exposure ratios other than 50/50 across uncorrelated ERC-20 assets. Treasury managers and on-chain index designs gain a tradable allocation without maintaining individual Uniswap v3 ranges. Curve StableSwap or a Balancer Stable Pool better matches assets intended to track one another closely. Concentrated-liquidity venues suit operators prepared to manage ranges, while a simple two-asset constant-product pool suits an equal allocation. The distinctive case remains a multi-asset 60/20/20 pool.

Limits, hooks, and edge cases

Put another way, Balancer’s advanced boundary lies where weighted math limits, token compatibility, custom hooks, and Vault-level controls meet the economics of a specific pool.

For context, Balancer’s weighted math caps the input used in one swap at 30% of the input-token balance and the output at 30% of the output-token balance. Non-proportional liquidity operations also keep the new-to-old invariant ratio between 70% and 300%. These are contract constraints, not recommended trade sizes. Price impact becomes material well before a hard limit when a reserve is shallow, so a quote and minimum-output setting remain essential.

Standard Weighted Pool weights stay fixed after deployment, and no token can sit below 1%. The v3 Vault works with standard ERC-20 assets; rebasing and double-entry-point token behavior is incompatible with its accounting model. Hooks expand a pool’s behavior by computing dynamic fees or adding callbacks around operations, yet they also add pool-specific logic that deserves inspection. Check the hook label, fee mode, token types, role accounts, pause state, and pool generation rather than inferring behavior from an 80/20 badge.

Pool limits belong to the pool type, while user-set slippage and transaction deadlines constrain each submitted action.

Withdrawal design matters at the edge. Proportional removal returns every underlying asset with zero pool-level price impact; a single-token removal embeds a rebalancing trade and charges the swap fee on its non-proportional portion. Deep liquidity, compatible tokens, and plain fixed-weight behavior make the standard path easier to model, all within the 70% invariant floor.