Gas & fees

Every amount on chain is an integer in uNRO: 1 NRO = 1 000 000 uNRO.

A fee is gas units × gas price, where the gas price is in uNRO per gas unit:

fee (uNRO) = gas_units × gas_price

Gas per operation

Operation	Gas units	Constant
Transfer	21	GAS_BASE_TRANSFER
Contract call (.app address with call data)	50 prepaid, then settled by actual use — see below	GAS_CONTRACT_CALL
Contract deploy	10 000, flat	DEPLOY_GAS_UNITS
Paid name transfer (.node, .vault, .agent)	flat 100 uNRO fee	NFT_TRANSFER_FEE
System operations (staking, registrations, faucet, governance markers)	0	—

At the minimum gas price of 1 uNRO, a transfer costs 21 uNRO = 0.000021 NRO.

Contract calls

A call is charged 50 gas units up front. The contract then runs in the WASM interpreter with a budget of 1 000 000 fuel (MAX_CONTRACT_GAS). After it finishes, the node converts the fuel actually burned into gas units — ceil(fuel / 20 000), at least 1 — and refunds or charges the difference.

The conversion rate is NEUROCHAIN_FUEL_PER_GAS_UNIT (default 20 000), chosen so a call that exhausts its fuel costs exactly the 50 units prepaid. Host functions such as storage reads and writes burn extra fuel; see NeuroWASM gas & limits.

If the contract traps or runs out of fuel, its storage changes are rolled back and the value is not transferred — but the nonce and the fee are still consumed, so a failing call cannot be replayed for free.

Base fee

The protocol keeps a base fee that moves with demand, in the style of Ethereum's EIP-1559:

• It starts at 1 uNRO per gas unit and never drops below that floor (MIN_GAS_PRICE).
• After each block, it moves towards a target of half the block gas budget (5 000 units): up when the block used more, down when it used less, by at most 12.5% per block. It always moves by at least 1 uNRO when it moves, so after congestion it returns all the way to the floor.
• A transaction whose gas_price is below the current base fee is rejected on every validator. This is enforced in consensus, not only by the mempool, so a proposer cannot slip an underpriced transaction past the others.

Read the current value before sending:

curl -s "$NODE_RPC/api/v1/gas/estimate"

{
  "base_fee": 1,
  "gas_base_transfer": 21,
  "gas_contract_call": 50,
  "estimated_transfer": 21,
  "estimated_contract": 50,
  "estimated_transfer_human": "0.000021",
  "estimated_contract_human": "0.00005",
  "total_burned": 0,
  "nft_transfer_fee": 100,
  "nft_transfer_fee_human": "0.0001"
}

The gateway serves the same data at $GATEWAY/api/v1/gas/estimate. The web wallet sends gas_price = base_fee × 1.5 to stay ahead of a rising base fee.

Where fees go

After each block, the sum of its fees is split:

• 50% is burned (BURN_RATE_BPS = 5000) and added to the running total_burned.
• 50% goes to the block's proposer.

Registration fees for .app and .vault names are burned in full; a .node registration becomes stake instead. See Addresses.

Block budget and the mempool

Rule	Default	Override	Notes
Gas per block	10 000 units	governance max_block_gas	1 to 1 000 000 000; read when the node starts
Transactions per block	500	—	MAX_BLOCK_TXS
Mempool size	10 000	NEUROCHAIN_MAX_MEMPOOL	When full, a new transaction pushes out the lowest-priced pending one — only if it pays more
Time in the mempool	60 seconds	—	A pending transaction not included by then is dropped
Pending per sender	64	NEUROCHAIN_MAX_PENDING_PER_ACCOUNT	Further transactions from the same address are refused
Replace by fee	+10%	NEUROCHAIN_RBF_MIN_BUMP_PCT	Re-sending the same (from, nonce) replaces the pending one only with a gas price at least this much higher
Mempool price floor	0 (off)	NEUROCHAIN_MIN_FEE_PER_GAS	Optional ingress floor on top of the base fee

The proposer takes pending transactions in fee order (same-sender transactions stay in nonce order), skips any below the base fee, and stops adding once the block budget is full. While choosing, it counts every transfer as 21 units and every .app call as 50.

Constants at a glance

Constant	Default	Meaning
UNRO_PER_NRO	1 000 000	uNRO in one NRO
GAS_BASE_TRANSFER	21	Gas units for a transfer
GAS_CONTRACT_CALL	50	Gas units prepaid for a contract call
DEPLOY_GAS_UNITS	10 000	Gas units for a deploy
MAX_CONTRACT_GAS	1 000 000	Fuel budget per contract call
NEUROCHAIN_FUEL_PER_GAS_UNIT	20 000	Fuel per gas unit when settling a call
MIN_GAS_PRICE	1	Base fee floor, uNRO per gas unit
MAX_BLOCK_GAS	10 000	Gas units per block
BURN_RATE_BPS	5 000	Share of fees burned, in basis points (50%)
NFT_TRANSFER_FEE	100	Flat fee for transferring a paid name, uNRO