Wei

Wei is the smallest, indivisible unit of Ether. 1 ETH = 10¹⁸ Wei = 1,000,000,000,000,000,000 Wei. Named after Wei Dai, the cryptographer whose 1998 b-money proposal is one of the conceptual ancestors of Bitcoin and the broader smart-contract ecosystem.

Smart contracts on Ethereum perform all balance arithmetic in integer Wei amounts. There’s no floating point on-chain — every value field, gas calculation, and balance is an unsigned 256-bit integer Wei value. ETH and Gwei are purely human-facing labels; the EVM only knows Wei.

In JavaScript this matters because Number.MAX_SAFE_INTEGERis roughly 9 × 10¹⁵. A 9 ETH balance is roughly 9 × 10¹⁸ Wei — three orders of magnitude past Number’s precision floor. Production wallet libraries use BigInt for Wei amounts. Our Wei / Gwei / ETH converter uses BigInt throughout so conversions round-trip without precision loss.