A cross-chain swap can arrive below its first estimate because pool prices move and each chain charges for its part of the transfer. To find the reason, compare the final output with the latest quote, then check the transaction record for fees and timing.
- Separate pool costs from network fees.
- Check whether the quote changed before execution.
- Use the final on-chain output to judge the trade.
What changes between a quote and delivery?
A quote estimates how much of the destination asset you should receive at that moment. It can change before the swap executes, especially when prices move or the trade is large compared with the available pool funds. A pool is a shared supply of two assets that traders swap against.
In a typical pool route, your input asset enters one pool, and the route may exchange it through another asset before reaching your destination. Each pool sets its price from the assets it holds. A large trade uses more of a pool’s available funds, which can move the price against your trade. Uniswap Developers describe this effect as price impact.
Cross-chain routes also need transactions on different networks. The source network processes the deposit; the destination network processes the payout. Network fees pay for those transactions, while a pool fee pays liquidity providers—the people who supply the assets traders swap. THORChain’s documentation describes one pool fee model as “slip-based,” meaning the fee depends on the trade’s size relative to pool depth.
how thor swap combines cross-chain steps helps explain why one trade can involve several network transactions under one route. For the same reason, check which amounts the quote already includes before adding fees yourself. Counting an included fee twice makes the shortfall look larger than it is.
How can you tell which cost reduced the amount?
Compare amounts in the destination asset first, then compare their value in dollars using the same price and time. For example, suppose a quote estimates 0.015 BTC, but the final transfer delivers 0.0147 BTC. At an illustrative BTC price of $66,667, that difference is about $20.
That $20 is not automatically a fee. The quote may have changed because the pool price moved before execution, or the route may include pool and network costs. Check the quote’s estimated output, any stated minimum output, and the transaction record’s actual payout. A transaction record is the public entry showing what a network processed.
Slippage means the difference between the expected and actual execution price. A slippage limit sets how much the price can worsen before a trade fails, if the route uses that protection. It does not guarantee the best price, and it is different from price impact: impact comes from your trade moving the pool price; slippage can also come from price changes while the trade is pending.
What should you check before trying again?
First, confirm that the destination transaction completed and that the receiving address is correct. If it is still pending, the final amount may not have arrived yet. Then compare the actual payout with the latest quote, rather than an earlier estimate or a dollar value from a different time.
If the output is lower than expected, look for pool fees, network fees, and price movement in the route details. If the transaction failed, check whether the route’s price limit was exceeded; a failed transaction is different from a completed swap with a smaller payout. The exact fee amounts vary by network, asset, pool depth, and route.
For a future trade, check the destination amount and the route’s minimum output immediately before you confirm. If the quote changes sharply or the minimum is too low for your needs, wait for a steadier price or choose a smaller amount. That check is the quickest way to decide whether to proceed with thor swap or review the route again.