What is the difference between the rate shown and the rate I actually get

05 September 2026

The rate shown on a swap preview is the mid-market rate - the average of current buy and sell prices on the exchanges the site uses. The rate you actually get is worse, because you are not buying at the midpoint; you are buying at the offer side of the spread, and the site adds a small margin on top.

Here is why the two numbers differ, and why the difference is not a trick.

The mid-market rate is a reference point, not a trade price

When you see a rate on the preview screen, it is calculated from the order book data the site receives from its liquidity providers. That data shows the best bid (the highest price someone will pay for a coin) and the best ask (the lowest price someone will sell it for). The mid-market rate sits exactly between them. No trade ever happens at that price. It is simply a snapshot of where the market is centered at that moment.

The spread is the real gap you cross

Every swap is executed at or near the ask price for the asset you are buying, and at or near the bid price for the asset you are selling. The distance between bid and ask is the spread. For a liquid pair like Bitcoin to USDC, the spread might be 0.1% or less. For an obscure token paired with a stablecoin, the spread can be 2% or more. That spread is the first thing that reduces the amount you receive compared to the mid-market preview.

The site adds a margin

On top of the spread, the site charges a fee - usually a fraction of a percent. That margin is how the site stays running. It is built into the swap rate, not added as a separate line item. The preview rate does not include this margin; the final rate does.

Liquidity depth changes the rate for larger swaps

If you are swapping a large amount relative to the liquidity available at the best ask, the swap will eat into deeper, less favorable orders. The average price you get will be worse than the top-of-book rate. The preview cannot always show this effect accurately because order books shift between the preview and the execution. The site will warn you if your swap size is large enough to cause significant slippage, but the rate you actually get may still be slightly worse than the preview suggested.

Network fees are separate

The rate difference discussed here is purely about the exchange rate. Network fees - the gas cost of sending the transaction on-chain - are shown separately and are not part of the rate comparison. Those fees go to miners or validators, not to the site.

Timing matters

The rate you see on the preview is valid for a few seconds. If you hesitate, the market moves. By the time you confirm, the bid and ask may have shifted. The site locks the rate at the moment of execution, not the moment of preview. A fast market can make the gap between preview and execution larger than the spread alone would explain.

How to read the real rate

The sibling page "How do I read a swap quote to see the real amount I will receive" shows you exactly where to look on the swap screen for the number that matters: the estimated output amount after all costs. That number already includes the spread and the site margin. It is the rate you will actually get if the market does not move.

Where to go next

If you want the full picture of what a swap actually costs - including network fees, spread, margin, and slippage - the hub page "What a crypto swap actually costs" ties all these pieces together. It explains why the total cost is never just the fee line.

The short answer: the preview rate is a clean reference. The real rate is that reference minus the spread, minus the site margin, and minus any slippage from order book depth. The difference is not hidden; it is just not shown in the preview number. You can see the real amount in the swap quote before you confirm.

Back to bridges