What is gas in a blockchain?
Gas in plain words
A blockchain is a shared ledger of transfers, copies of which are kept by many computers on the network. New entries are added to it by miners and validators, that is, participants whose computers check transfers. The network fee pays for this work. The network itself charges it, so the fee exists even when you send crypto from your own wallet to someone else's, with no exchange and no middlemen.
The name comes from Ethereum. A car needs gasoline to drive, and in the same way an operation needs gas so that the network can process it. On Ethereum, gas is the unit that measures how much work the network's computers do on an operation1, and in everyday speech the fee itself is called gas too.
Usually the fee goes to miners or validators, although on Ethereum part of the payment is burned, that is, destroyed forever1. Bitcoin does not use the word "gas"; there it is simply a transfer fee, and the miner receives it2.
Why the fee is paid in the network coin
A network takes payment in its own coin. The Ethereum network accepts fees only in ETH1, and on Solana every operation is paid for in SOL3. The same rule applies to tokens, that is, crypto issued on top of someone else's network. USDT on Ethereum is run by a smart contract, a program inside the network; such programs are explained in smart contract. Sending USDT is an operation with this smart contract, and the network charges ETH for it. The network itself does not accept fees in USDT. Why a token has no network of its own is explained in what is a token.
On Tron, instead of a money fee, the network deducts resources from your address (your "account" on the network), and sending USDT needs "energy"45. If the address has no energy, the network burns a little TRX from the sender's address4. How to get energy in advance and burn less TRX is described below, in the section on lowering the fee.
What to do if your wallet has no network coin
If there is no network coin at the address, or less than the fee requires, the token transfer will not go through. The token stays at your address and nothing is lost; you just need to top up the address. Here is the order:
- Check in your wallet which network the token is on, for example USDT on the Tron network or on the Ethereum network.
- Top up that same address with a small amount of that network's coin: TRX for Tron or ETH for Ethereum. You can buy the coin on an exchange and withdraw it to your address, choosing the same network when you withdraw, or ask someone you know to send it to you.
- Wait for the coin to arrive, then send the token. Your wallet will show the fee before you confirm.
If your wallet can take the fee in a token on that network, you can skip the second step. The guide how to send USDT walks through sending USDT step by step.
How to lower the fee or pay it in another cryptocurrency
Which of the five ways suits you depends on the network and the wallet.
Choose a network with a lower fee
Pick a cheaper network only if the recipient supports it. A transfer on a network the recipient does not use may never reach them, and the fee you saved turns into the loss of the whole amount. How to choose a network is covered in the guide how to send crypto, and networks for USDT are compared in how to send USDT.
Send when the network is less busy
Where the fee depends on network load, as on Ethereum, a non-urgent operation is cheaper to put off until the network is quieter. Many wallets let you choose the speed. In MetaMask, for example, the "Low" option costs less, but the operation will most likely take longer7.
Do not change the fee settings your wallet set on its own unless you understand them. If the gas you paid for runs out before the operation finishes, the network cancels its result but still keeps the fee spent1.
Get energy on the Tron network
Energy covers the smart contract's work when you send USDT on Tron, and if your address has enough of it, the network does not burn your TRX for the fee8. There are two ways to get energy. You can put your own TRX up as a deposit (staking): the coins stay yours, and you can take them back out after a waiting period set by the network8. Or you can receive energy from another address. Its owner stakes their own TRX and passes the resulting energy to your address, while the TRX stays with them9. Third-party services that rent out energy for a fee work this way too.
Before paying such a service, check its website address and look for reviews of it on other platforms. To pass you energy, a service needs only your wallet address. Never share your seed phrase or private key with anyone, and if a service asks you to sign a permission for your tokens, refuse.
Pay the fee with a token through your wallet
Some wallets and apps on certain networks pay the fee for you or take it in a token you hold at your address10. As of 30.10.2026, MetaMask on some networks offers on its own to pay the fee in another token, such as USDT, when your wallet is low on the network coin, and charges a small fee for this11. Trust Wallet's FlexGas feature lets you pay the fee in USDT, USDC and its own TWT token on some networks12. On 30.10.2026 the Tron network was not on these lists. Which networks and tokens your wallet supports is in its help pages.
Withdraw from an exchange
If your crypto sits on an exchange, withdrawing it requires no network coin. How the transfer is paid for in that case is answered in the FAQ.
What the size of the fee depends on
Three things decide how much you pay: how much work the operation takes, how busy the network is, and which network you use.
A swap or another smart contract action takes more work than a simple ETH transfer, so it uses more gas1. The amount sent is not part of the calculation, and on Bitcoin sending a large sum can cost the same as sending a small one2.
Network load works like taxi fares at rush hour. Space in a block, the next batch of entries, is limited, and when there are many operations, senders offer a bigger tip so that theirs is taken sooner. On Ethereum and Bitcoin the price rises in exactly this way along with demand for space in blocks12.
The network changes the price as well. The same token, USDT for example, is issued on different networks, and a transfer costs a different amount on each; token standards covers this in detail. There are also layer-2 networks such as Base and Arbitrum, separate networks on top of Ethereum where transfers are cheaper and the results are written to Ethereum1. What an operation on a network costs right now is shown by a block explorer, a website where you can see transfers and the current gas price.
More detail on how fees are calculated on Ethereum and Tron
A standard ETH transfer requires 21,000 units of gas. The fee equals the number of units used multiplied by the price of one unit1. On Ethereum the price of a unit of gas is made up of a base fee, which is burned and leaves circulation, and a tip, which goes to the validator that added the operation to a block1. The base fee rises by itself when blocks are full and falls when they are half empty1.
Besides energy, Tron has a second resource, bandwidth, which covers the size of an operation45. Every address gets a little bandwidth for free, which refills within a day, while energy is never given for free4.
