Why your swap preview shows a different amount than what you receive

05 September 2026

The swap preview shows an estimate, not a guarantee. What you receive is determined by the state of the pool the moment your transaction executes, which can differ from the state when you first loaded the preview.

This discrepancy is most common when swapping low-liquidity tokens - the subject of the hub page "Swapping in and out of memecoins." Here is why it happens.

Liquidity depth is the core issue. A swap preview calculates the expected output using the current reserves in the liquidity pool. Those reserves are a snapshot. Between the moment you see the preview and the moment your transaction is confirmed on-chain, other traders can move tokens in or out of that pool. If someone else buys before you, the price moves against you, and you receive less. If someone sells, the price moves in your favor, and you receive more. In low-liquidity pools, even a single small trade can shift the price significantly.

The preview does not account for your own price impact. When you enter an amount to swap, the preview estimates the output assuming no other trades happen. But your own trade is itself a large event in a shallow pool. The preview might show a static calculation, but the actual execution includes your own slippage. Many interfaces show a "minimum received" figure that accounts for your price impact plus a small buffer. The "preview" number often ignores that buffer entirely.

Gas and network congestion add latency. The preview is a client-side calculation based on data that may be seconds old. In fast-moving markets, those seconds matter. A memecoin with a few thousand dollars of liquidity can see its price change 10-20% in the time it takes to sign and broadcast a transaction. The preview cannot predict that.

The swap contract may apply additional fees. Some tokens have transfer taxes, buy/sell fees, or reflection mechanisms. The preview might not include those deductions. The actual receipt subtracts them. For tokens with a 5% tax, the preview and the received amount will always differ by at least that percentage.

Dead or near-dead tokens exaggerate the gap. If a token has no active trading pair or only one seller at a very high price, the preview may show an output based on that single order. But that order might be cancelled or front-run before your transaction lands. The received amount then becomes zero or a fraction of the preview. This is covered in more detail on the sibling page "Why a token shows a price but your swap keeps failing."

What you can do. Set a realistic slippage tolerance - typically 1-5% for liquid tokens, but up to 15-20% for very shallow memecoin pools. Accept that the preview is a rough guide, not a quote. If the difference between preview and receipt consistently exceeds your slippage tolerance, the token likely lacks enough buyers to sell into. That scenario is addressed on the sibling page "How to tell if a token has enough buyers to sell into."

The preview is a convenience, not a promise. The received amount is reality. In low-liquidity markets, those two numbers rarely match.

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