Keep TRX in the wallet that sends your first swap. The amount depends on the contract calls and network resources available, so there is no fixed fee. Check the transaction’s estimate and leave enough TRX to cover the part your resources do not cover.
A wallet-connected service such as the TRON swap app trades TRX or TRON tokens from your wallet. TRC-20 tokens, such as USDT and JST, are tokens made for the TRON network, and their swaps still need network resources.
1. What uses TRX during a token swap?
TRX can pay the network cost of running the swap. A swap usually calls a smart contract, which is a program on TRON that carries out the trade.
TRON measures network use with Bandwidth and Energy. Bandwidth covers the size of a transaction; Energy covers the computing work a contract performs. You can get these resources by staking TRX or receiving them from another account. If you do not have enough, the network can burn TRX from your wallet to cover the shortfall.
2. How can you estimate the fee?
Check the Energy estimate and how much Energy your wallet already has. Energy is the resource a contract call needs, and there is no free Energy allowance. At the current documented rate, uncovered Energy costs 100 sun per unit; one TRX equals one million sun.
For example, if a call needs 100,000 Energy and none is covered by your resources or the contract operator, the Energy charge would be 10 TRX. That is an illustration, not a quote for a particular swap. The amount can change with the token, the trade route, your available resources, and whether the contract operator covers part of the cost.
Bandwidth can add a smaller charge if your free allowance or staked amount is used up. TRON currently gives each account 600 free Bandwidth per rolling 24-hour period. A swap uses a contract call, so do not assume that free Bandwidth will cover its Energy cost.
3. How much TRX should you leave in your wallet?
Leave at least the estimated uncovered network cost, plus a small buffer if the estimate may change. The transaction’s estimate is more useful than a memorized balance because contract routes and your remaining Energy can differ. Check that estimate before you confirm a TRON swap.
A common mistake is to spend all your TRX buying USDT, then discover the wallet has no TRX left for the trade’s network cost. Keep some TRX aside in the sending wallet; the token you are swapping does not automatically pay that cost. Also check that the wallet is set to TRON and that the token is the one you intend to trade. If the swap fails after contract execution begins, some Energy may still be charged.
Your next step is to check the transaction estimate and your wallet’s available TRX and Energy. If the balance cannot cover the uncovered cost, add TRX or wait until you have enough resources before sending the swap.
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