Wei

Wei is the base unit of value on the Ethereum network: every other denomination, including Ether itself, is just a multiple of it. The name honors Wei Dai, a cypherpunk cryptographer whose 1998 "b-money" proposal helped lay the theoretical groundwork for digital cash long before Bitcoin or Ethereum existed.

Because Wei has no decimal places, Ethereum's software and smart contracts can represent any amount as a plain integer. This matters more than it might seem: computers handle whole numbers exactly, but decimal (floating-point) math can introduce tiny rounding errors. By expressing balances and transfers in Wei internally, the Ethereum Virtual Machine avoids those errors entirely, which is essential when contracts are moving real value.

In practice, almost nobody quotes prices or balances in raw Wei, since the numbers involved are unwieldy (1 ETH equals a quintillion Wei). Instead, most user-facing tools display balances in ETH and price network fees in a mid-sized unit called Gwei, which equals one billion Wei. Gwei is the standard unit for quoting gas prices, the fee paid to validators for processing a transaction or executing a contract.

Developers still work with Wei directly at the code level, since Ethereum libraries and APIs typically accept and return values in Wei to guarantee precision. Wallets and block explorers convert these figures automatically for display.