DEX swaps: slippage, price impact and minimum received

Price impact and slippage answer different questions about a decentralized exchange swap. Price impact describes how a trade affects pool pricing. Slippage compares the quoted outcome with the eventual execution. A minimum-received amount sets an execution constraint. Confusing the three can make a disappointing quote look acceptable simply because the slippage percentage is small.

The distinctions below use Uniswap's documentation and a hypothetical exact-input swap. Interfaces and trading mechanisms differ, so the final confirmation screen and the transaction's actual conditions matter more than a familiar label.

Start with three separate questions

Uniswap's comparison of price impact and slippage identifies price impact as the price change caused by the trade itself. It defines slippage as the difference between the expected and received outcome.

That gives three useful questions: What does this trade do to pricing? How much worse may execution become after the quote? What actually arrived? The first concerns the quote and liquidity; the second concerns an instruction; the third concerns a completed transaction.

The tolerance is permission, not an additional fee charged automatically. A 1% tolerance does not mean every completed trade loses 1% of its quoted output.

Price impact can already be in the quote

An automated market maker exchanges tokens against liquidity. Uniswap's price-impact explanation connects the trade's effect to liquidity depth: the same trade can have a larger effect in a shallow pool than in a deeper one. Current liquidity and trade size are therefore part of interpreting the quoted exchange rate.

Consider a hypothetical preview in which a tiny reference trade suggests 500 output tokens for the proposed input, but the full-size quote offers 485. If we deliberately exclude every fee and hold the reference comparison constant, the 15-token difference illustrates a 3% reduction associated with trade size.

In a real interface, the reference price and fee treatment may differ. The point of the example is the sequence: the full-size quote is already 485. Setting a tight tolerance around it cannot restore the hypothetical 500-token reference. Raising tolerance cannot deepen the pool either.

Read minimum received as an amount

For an exact-input swap, the input is fixed and the output varies. Uniswap's V3 swap documentation exposes an amountOutMinimum parameter for this protection. For an exact-output swap, the desired output is fixed and the corresponding protection is a maximum input amount.

Suppose a hypothetical interface quotes 485 tokens and explicitly calculates its 1% tolerance as a haircut to quoted output. Its minimum would be:

485 × (1 − 0.01) = 480.15 tokens.

That arithmetic applies to the stated hypothetical convention. Uniswap's V2 SDK also calculates an output haircut, with amounts rounded to token units. Do not generalize from this example to every interface or order type: read the minimum displayed for the actual transaction.

Under these assumed conditions, 482 tokens would satisfy the minimum, while 479 would not. An enforceable floor determines which execution is acceptable; it does not promise that the transaction will execute. Nor does it measure the difference from the earlier 500-token reference.

What can change before execution

Uniswap's slippage explainer describes market movement while a transaction waits for confirmation and adverse transaction ordering, including sandwich activity. These can change the outcome after a quote was obtained.

A tighter permitted deviation can reject more outcomes. A wider one allows worse outcomes to pass. That trade-off does not identify a universally correct percentage, and simply increasing tolerance after a failure does not explain why the previous attempt failed.

The same explainer notes that a failed onchain swap can still incur network costs. Token output, swap fees and network costs therefore belong in separate fields when reviewing an attempt. A rejected execution is not automatically a costless event, and a successful execution is not automatically a good exchange rate.

Not every swap uses adjustable slippage

A familiar application can offer different execution mechanisms. In its UniswapX guidance, Uniswap states that the usual non-UniswapX slippage settings do not apply to UniswapX swaps. The minimum amount remains visible.

This matters when comparing screenshots or following instructions written for another route. Before interpreting a percentage, identify whether the trade is a conventional pool swap or a different order mechanism. Do not assume that changing a setting in one mode changes conditions in another. A visible minimum is useful only when paired with the exact order being authorized.

A worksheet for comparing quote and receipt

The following worksheet is an original recordkeeping example, using the hypothetical quote above. It separates observations from calculations and leaves cost fields explicit.

The 0.619% figure is an output-quantity comparison. Calling it a change in price requires stating which token is the denominator. Recording both raw token amounts avoids an ambiguous percentage.

To compare two routes, use the same input amount, output token, chain and observation time as closely as possible. Record whether each number is an estimate, an enforceable limit or a confirmed receipt. If those categories differ, a side-by-side percentage comparison can be misleading before any trade occurs.

A completed swap answers a narrow question: an exchange executed under certain conditions. It does not establish the output token's backing or redemption rights. For stablecoin pairs, our explanation of reserves, redemption and the peg addresses that separate question.

Source review: 22 September 2026. All numerical scenarios are hypothetical.