What is Price Impact?
Price impact measures how much your trade will move the market price of an asset. It represents the difference between the current market price and the average price you will receive when executing your trade. Larger trades relative to available liquidity cause greater price impact, resulting in less favorable execution prices.
Understanding Price Impact Mechanics
In automated market maker systems, prices are determined by the ratio of assets in liquidity pools. When you swap one token for another, you are adding one asset to the pool and removing another. This changes the ratio and thus the price.
For example, in a constant product AMM using the formula x times y equals k, buying ETH with USDC adds USDC to the pool and removes ETH. This increases the ETH price within the pool. The more you buy relative to pool depth, the higher the price rises during your trade.
Calculating Price Impact
Price impact is typically displayed as a percentage on DEX interfaces. A 1% price impact means your effective execution price is 1% worse than the current spot price due to your trade size affecting the pool.
The relationship between trade size and price impact is not linear. Doubling trade size more than doubles price impact in most AMM designs. This makes splitting large trades into smaller pieces or routing through multiple pools often more efficient for overall execution.
Price Impact vs. Slippage
While related, price impact and slippage are distinct concepts. Price impact is the expected, calculable effect of your trade size on price. Slippage is the unexpected price movement between transaction submission and execution. DEXs show expected price impact before you confirm the trade, while slippage depends on market movements during confirmation.
Minimizing Price Impact
Several strategies can reduce price impact. Using DEX aggregators like 1inch or Paraswap routes trades through multiple pools and protocols to find the best overall price. Splitting large trades into smaller transactions executed over time using TWAP strategies reduces per-trade impact. Trading on pools with higher liquidity naturally reduces impact for any given trade size.
For very large trades, over-the-counter desks or request-for-quote systems can provide better execution than on-chain pools.