Back After Months? Choose the Swap Amount to Lock

If you’re returning after months away, the amount you type last is the fixed side: enter a sell amount to lock what you spend, or a receive amount to lock what you get. The other side can move within your slippage tolerance, so the field you edit—and the bound shown beside the quote—tell you what the trade is allowed to do.

The last field you edit selects the swap mode

Typing into the sell field creates an exact-input swap: the amount of the token you send is fixed, and the amount you receive is estimated. Typing into the receive field creates an exact-output swap: the amount you want to receive is fixed, and the amount needed to buy it is estimated. If you edit the receive field after entering a sell amount, the interface switches modes, even if the screen still looks like the same trade.

That switch changes which risk the quote limits. With exact input, the router spends the specified input and requires the output to meet a minimum. With exact output, it aims to deliver the specified amount and refuses to spend more than a maximum. SunSwap V2’s Router functions use these same two patterns: its exact-input function takes an input amount and a minimum output, while its exact-output function takes an output amount and a maximum input.

If you need to budget the wallet-level result around another payment, how SunSwap sets spend and receipt is the broader question; the slippage bound is the specific limit that helps shape that result. The quote is an estimate based on the pool’s current state. While the transaction is waiting, trading can change that state, so the final receipt or spend may differ from the estimate without crossing the bound.

“Minimum received” limits an exact-input swap

When the quote says “Minimum received,” the sell amount is fixed and the receipt is the side that can vary. You are telling the router how much to sell, then setting the least output you will accept if the price moves before execution. The estimate can improve, but if the output would fall below that minimum, the swap should fail instead of completing at a worse rate.

The minimum is approximately the quoted output multiplied by one minus your slippage tolerance. For example, a 1% tolerance makes the minimum about 99% of the quoted output. The percentage is the setting you choose; it is not an extra amount paid to the pool. A wider tolerance lowers the minimum and allows more movement before the transaction fails, while a narrower one sets a stricter floor.

Choose exact input when the amount you are willing to sell matters most, such as when spending a particular amount of TRX or a TRC-20 token. The output is not guaranteed to match the estimate, but the minimum shows the cutoff. Pressing Max on the sell side fills the full available token balance and keeps the swap in exact-input mode; it does not turn the trade into a request for a precise amount out.

“Maximum sold” caps an exact-output swap

When the quote says “Maximum sold,” the receive amount is fixed and the spend is allowed to vary up to a ceiling. You are asking for a specific amount of the output token. The router calculates the input needed and permits the transaction only if that requirement stays at or below your maximum.

The maximum is approximately the quoted input multiplied by one plus your slippage tolerance. At 1%, for instance, the cap is about 101% of the quoted input. If the pool price moves and buying the requested output would cost more than that cap, the swap should fail. If it costs less, only the amount needed is spent; unused input remains in your wallet.

Choose exact output when receiving a particular amount matters more than spending a particular amount, such as when you need a set quantity for a planned use. Read “Maximum sold” as a limit, not as the amount the trade will certainly take. If the receive field is the last one you edited, that is the mode and bound to pay attention to.

Fee-on-transfer tokens need exact input

For a token that deducts a fee when it is transferred, use exact input if the router offers the supported route. The amount that arrives at the pool can be less than the amount sent, so a route that assumes the full input arrives may calculate the swap incorrectly. The fee-supporting exact-input router functions account for the amount received and still enforce a minimum output; they do not provide the matching exact-output route.

The SunSwap V2 Interface Documentation describes the router’s “SupportingFeeOnTransferTokens” functions as applicable to tokens that charge transfer fees. Its Router section also distinguishes fixed input with a minimum output from fixed output with a maximum input. That is the mechanism behind the labels: before confirming, look at the field you last edited, then make sure the displayed minimum or maximum is the limit you intend to accept.