What is the smallest unit of Ethereum?

Wei as the Base Unit

1. Wei is the smallest denomination of Ether, the native cryptocurrency of the Ethereum network.

2. One Ether equals 1,000,000,000,000,000,000 Wei — a total of 10¹⁸ Wei per Ether.

3. All transaction fees, gas prices, and internal accounting within Ethereum’s virtual machine operate exclusively in Wei.

4. Developers interacting with smart contracts or sending raw transactions must specify gas price and value in Wei to ensure precision and avoid rounding errors.

5. Wallets and explorers often abstract Wei into higher denominations like Gwei or Ether for user convenience, but the protocol layer never uses those units directly.

Common Denominations in Practice

1. Gwei — short for gigawei — equals 1,000,000,000 Wei and is the standard unit used when setting gas prices.

2. Mwei, Kwei, and other intermediate units exist but are rarely used outside of low-level debugging or testing environments.

3. The Ethereum JSON-RPC API always expects values in Wei, requiring developers to convert human-readable inputs before submission.

4. Block explorers display transaction values in Ether by default but allow toggling to Wei for forensic analysis of contract interactions.

5. Gas cost calculations during contract execution rely on Wei-based arithmetic to maintain deterministic outcomes across all nodes.

Why Precision Matters

1. Smart contract logic may involve micro-payments, fee splits, or interest accrual over time — all of which require sub-wei-level accuracy in design, even if final outputs round to whole Wei.

2. Reentrancy protections and balance checks depend on exact Wei comparisons; floating-point approximations would break consensus guarantees.

3. Token standards like ERC-20 define decimal places separately, but underlying transfers still occur in Wei-equivalents after applying the token’s specified precision.

4. Mining rewards and uncle inclusion incentives are denominated in Wei to preserve fairness across varying block intervals and network conditions.

5. Off-chain scaling solutions such as state channels or rollups inherit this Wei-centric model when settling final balances on Layer 1.

Gas Pricing and Wei

1. The base fee per gas unit is quoted in Wei and dynamically adjusted based on network congestion using an EIP-1559 mechanism.

2. Users can set a priority fee (also in Wei) to incentivize miners or validators to include their transactions faster.

3. Total transaction cost equals (base fee + priority fee) multiplied by gas used — all computed in Wei before conversion to Ether for display.

4. Historical gas price data tracked by analytics platforms is stored and indexed in Wei to support consistent time-series analysis.

5. Wallet interfaces that auto-suggest gas prices fetch real-time Wei values from node providers rather than estimating in Ether and converting backward.

Frequently Asked Questions

Q: Can a transaction be sent with a value less than one Wei?A: No. The Ethereum protocol enforces integer Wei values. Fractional Wei cannot exist on-chain.

Q: Is Wei used in Ethereum Classic or other forks?A: Yes. Ethereum Classic retains the same denomination structure, including Wei as its atomic unit.

Q: Do Layer 2 networks like Arbitrum or Optimism use Wei?A: They adopt the same unit system for compatibility; native token transfers and gas accounting remain expressed in Wei internally.

Q: Why not use Satoshi-style naming for Wei?A: Wei honors cryptographer Wei Dai, whose b-money proposal influenced early blockchain concepts — a deliberate tribute embedded in Ethereum’s foundational design.