The transaction fee for the current Klaytn virtual machine (KLVM) is computed as follows:

Transaction fee := (total gas used) x (unit price)

The

`total gas used`

is computed by KLVM based on the gas cost of the opcode and the intrinsic gas cost.`unit price`

is the price of gas defined in Klaytn.

This calculated transaction fee is subtracted from the sender's or enterprise account's balance, depending on the transaction.

Every action that changes the state of the blockchain requires gas. When a node processes user's transaction such as sending KLAY, using ERC-20 tokens, or executing a contract, the user has to pay for the computation and storage usage. The amount of payment is decided by the amount of `gas`

required.

`Gas`

is a measuring unit representing how much calculation is needed to process the user's transaction.

`Unit price`

is the price for a single gas. The unit price (also called `gas price`

) is set in the system by the governance. It is currently set to 25 Gpeb (*i.e.*, 25 x 10^9 peb) per gas and cannot be changed by user. The current value of the unit price can be obtained by calling the `klay.gasPrice`

API.

In Ethereum, users set the gas price for each transaction, and miners choose which transactions to be included in their block to maximize their reward. It is something like bidding for limited resources. This approach has been working because it is market-based. However, the transaction cost fluctuates and often becomes too high to guarantee the execution.

To solve the problem, Klaytn is using a fixed unit price and the price can be adjusted by the governance council. This policy ensures that every transaction will be handled equally and be guaranteed to be executed. Therefore, users do not need to struggle to determine the right unit price.

Klaytn only accepts transactions with gas prices, which can be set by the user, that are equal to the unit price of Klaytn; it rejects transactions with gas prices that are different from the unit price in Klaytn.

The error message `invalid unit price`

is returned when the gas price of a transaction is not equal to the unit price of Klaytn.

Klaytn currently does not provide a way to replace a transaction using the unit price but may support different methods for the transaction replacement in the future. Note that in Ethereum, a transaction with a given nonce can be replaced by a new one with a higher gas price.

Basically, Klaytn is keeping compatibility with Ethereum. So Klaytn's gas table is pretty similar with that of Ethereum. But because of the existence of unique features of Klaytn, there are several new constants for those features.

Item | Gas | Description |

G_zero | 0 | Nothing paid for operations of the set Wzero |

G_base | 2 | Amount of gas to pay for operations of the set Wbase |

G_verylow | 3 | Amount of gas to pay for operations of the set Wverylow |

G_low | 5 | Amount of gas to pay for operations of the set Wlow |

G_mid | 8 | Amount of gas to pay for operations of the set Wmid |

G_high | 10 | Amount of gas to pay for operations of the set Whigh |

G_blockhash | 20 | Payment for BLOCKHASH operation |

G_extcode | 700 | Amount of gas to pay for operations of the set Wextcode |

G_balance | 400 | Amount of gas to pay for a BALANCE operation |

G_sload | 200 | Paid for a SLOAD operation |

G_jumpdest | 1 | Paid for a JUMPDEST operation |

G_sset | 20000 | Paid for an SSTORE operation when the storage value is set to non-zero from zero |

G_sreset | 5000 | Paid for an SSTORE operation when the storage value’s zeroness remains unchanged or is set to zero |

G_sclear | 15000 | Refund given (added into refund counter) when the storage value is set to zero from non-zero |

R_selfdestruct | 24000 | Refund given (added into refund counter) for self-destructing an account |

G_selfdestruct | 5000 | Amount of gas to pay for a SELFDESTRUCT operation |

G_create | 32000 | Paid for a CREATE operation |

G_codedeposit | 200 | Paid per byte for a CREATE operation to succeed in placing code into state |

G_call | 700 | Paid for a CALL operation |

G_callvalue | 9000 | Paid for a non-zero value transfer as part of the CALL operation |

G_callstipend | 2300 | A stipend for the called contract subtracted from Gcallvalue for a non-zero value transfer |

G_newaccount | 25000 | Paid for a CALL or SELFDESTRUCT operation which creates an account |

G_exp | 10 | Partial payment for an EXP operation |

G_expbyte | 50 | Partial payment when multiplied by dlog256(exponent)e for the EXP operation |

G_memory | 3 | Paid for every additional word when expanding memory |

G_txcreate | 32000 | Paid by all contract-creating transactions |

G_transaction | 21000 | Paid for every transaction |

G_log | 375 | Partial payment for a LOG operation |

G_logdata | 8 | Paid for each byte in a LOG operation’s data |

G_logtopic | 375 | Paid for each topic of a LOG operation |

G_sha3 | 30 | Paid for each SHA3 operation |

G_sha3word | 6 | Paid for each word (rounded up) for input data to a SHA3 operation |

G_copy | 3 | Partial payment for *COPY operations, multiplied by words copied, rounded up |

G_blockhash | 20 | Payment for BLOCKHASH operation |

G_extcodehash | 400 | Paid for getting keccak256 hash of a contract's code |

G_create2 | 32000 | Paid for opcode CREATE2 which bahaves identically with CREATE but use different arguemnts |

Precompiled contracts are special kind of contracts which usually perform complex cryptographic computations and are initiated by other contracts.

Item | Gas | Description |

EcrecoverGas | 3000 | Perform ECRecover operaton |

Sha256BaseGas | 60 | Perform sha256 hash operation |

Sha256PerWordGas | 12 | |

Ripemd160BaseGas | 600 | Perform Ripemd160 operation |

Ripemd160PerWordGas | 120 | |

IdentityBaseGas | 15 | |

IdentityPerWordGas | 3 | |

ModExpQuadCoeffDiv | 20 | |

Bn256AddGas | 500 | Perform Bn256 elliptic curve operation |

Bn256ScalarMulGas | 40000 | |

Bn256PairingBaseGas | 100000 | |

Bn256PairingPerPointGas | 80000 | |

VMLogBaseGas | 100 | Write logs to node's log file - Klaytn only |

VMLogPerByteGas | 20 | Klaytn only |

FeePayerGas | 300 | Get feePayer's address - Klaytn only |

ValidateSenderGas | 5000 per signature | Validate the sender's address and signature - Klaytn only |

Total gas of those items which has XXXBaseGas and XXXPerWordGas (e.g. Sha256BaseGas, Sha256PerWordGas) are calcluated as

TotalGas = XXXBaseGas + (number of words * XXXPerWordGas)

ValidateSenderGas have to be paid per signature basis.

TotalGas = number of signatures * ValidateSenderGas

Item | Gas | Description |

TxAccountCreationGasPerKey | 20000 | Gas required for a key-pair creation |

TxValidationGasPerKey | 15000 | Gas required for a key validation |

TxGasAccountUpdate | 21000 | Gas required for an account update |

TxGasFeeDelegated | 10000 | Gas required for a fee delegation |

TxGasFeeDelegatedWithRatio | 15000 | Gas required for a fee delegation with ratio |

TxGasCancel | 21000 | Gas required to cancel a transaction which has a same nonce |

TxGasValueTransfer | 21000 | Gas required to transfer KLAY |

TxGasContractExecution | 21000 | Base gas for contract execution |

TxDataGas | 100 | Gas required per transaction's single byte |

Gas for payload data is calculated as below

GasPayload = number_of_bytes * TxDataGas

TxType | Gas |

LegacyTransaction | TxGas + PayloadGas + KeyValidationGas |

ValueTransfer | TxGasValueTransfer + KeyValidationGas |

ValueTransferMemo | TxGasValueTransfer + PayloadGas + KeyValidationGas |

AccountUpdate | TxGasAccountUpdate + KeyCreationGas + KeyValidationGas |

SmartContractDeploy | TxGasContractCreation + PayloadGas + KeyValidationGas |

SmartContractExecution | TxGasContractExecution + PayloadGas + KeyValidationGas |

Cancel | TxGasCancel + KeyValidationGas |

KeyValidationGas is defined as below based on key type,

Key Type | Gas |

Nil | N/A |

Legacy | 0 |

Fail | 0 |

Public | 0 |

MultiSig | (keys-1) * GasValidationPerKey (15000) |

RoleBased | Based on keys in the role used in the validation |

KeyCreationGas is defined as below based on key type,

Key Type | Gas |

Nil | N/A |

Legacy | 0 |

Fail | 0 |

Public | GasCreationPerKey (20000) |

MultiSig | (keys) * GasCreationPerKey |

RoleBased | Gas fee calculated based on keys in each role. e.g., GasRoleTransaction = (keys) |