Wei

Beginner
Updated Aug 24, 2026

What Is Wei?

Wei is the smallest denomination of ether (ETH), the native currency of the Ethereum network. One ether equals one quintillion wei (10^18 wei).
Named after Wei Dai, a computer scientist known for his contributions to cryptography and the creation of b-money, wei serves as the base unit for all transactions and calculations on Ethereum. The Ethereum protocol does not use fractions of a wei, so all values on the network are expressed in whole wei integers.

How Wei Works on Ethereum

Because Ethereum handles very small transactions, using ether as the primary unit can be impractical. Gas fees, for example, are typically measured in gwei (short for gigawei), where one gwei equals one billion wei (10^9 wei or 0.000000001 ETH). This makes gwei a more convenient unit for discussing transaction costs, while wei remains the fundamental unit the protocol uses for precise calculations.
When a user sends ETH or interacts with a smart contract, the network processes the transaction in wei, even though wallet interfaces usually display balances in ether. This means that behind every ETH transfer, the actual value being moved is an integer expressed in wei.

Ether Denominations

Wei is part of a broader system of ether denominations, each representing a different power of ten. The table below shows the main units:

Unit

Wei value

Wei

Ether Value

Wei

1 wei

1

10-18 ETH

Kwei

10^3 wei

1,000

10-15 ETH

Mwei

10^6 wei

1,000,000

10-12 ETH

Gwei

10^9 wei

1,000,000,000

10-9 ETH

Microether

10^12 wei

1,000,000,000,000

10-6 ETH

Milliether

10^15 wei

1,000,000,000,000,000

10-3 ETH

Ether

10^18 wei

1,000,000,000,000,000,000

1 ETH

Among these, gwei and ether are the most frequently used. Gwei is the standard unit for quoting gas prices, while ether is the default unit for displaying balances and transfer amounts in user-facing applications.

Why Wei Matters

Wei matters because it provides the precision the Ethereum network needs to function. Without a sufficiently small base unit, the network could not accurately represent the tiny values involved in gas fee calculations, smart contract operations, and microtransactions. By using wei as the foundational unit, Ethereum ensures that all value transfers are exact and consistent across the entire network.

Similar to how Bitcoin uses the satoshi as its smallest unit (1 satoshi = 10^-8 BTC), Ethereum uses wei to enable granular value representation. This design supports a wide range of applications, from large transfers to automated smart contract interactions that may involve very small amounts of ETH.
Learn more: What Is Ethereum?
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