# Transaction Fee Gas refers to the transaction fee that will be charged to any transaction or execution on the Smart Contract in KardiaChain network. Gas is measured in HYDRO. 1KAI = 10^18 HYDRO 1 OXY = 10^9 HYDRO = 0.000000001 KAI A transaction fee will be calculated by the following formula: gasFee = gasPrice \* gasLimit The minimum gasPrice is 1 OXY (or 1000000000 HYDRO) The minimum gasLimit is 29000 and the maximum gasLimit is 20000000
A typical transaction gas limit for sending KAI on the network is 29000 1000000000 \* 29000 = 29000000000000 HYDRO = 0,000029 KAI A smart contract operation or any transaction on KardiaChain network will cost gas for computing the logic in KVM. * It costs zero fee to read data from a smart contract. * Gas will return to users if a smart contract execution does not spend all the gas fee. * If the transaction is processed but not enough gas to pay, it will be dropped (failed) and gas won't be returned.