Wei
The smallest unit of Ether (ETH), equal to 10^-18 ETH. Named after Wei Dai, a cryptography pioneer, wei is used for precise calculations in Ethereum smart contracts.
Last updated: January 5, 2025
What is Wei?
Wei is the smallest denomination of Ether (ETH), similar to how a cent is the smallest unit of a dollar. One Ether equals 1,000,000,000,000,000,000 wei (10^18 wei). The unit is named after Wei Dai, a computer engineer and cryptography pioneer.
Ethereum Denominations
| Unit | Wei Value | ETH Value |
|---|---|---|
| Wei | 1 | 0.000000000000000001 |
| Gwei | 10^9 | 0.000000001 |
| Finney | 10^15 | 0.001 |
| Ether | 10^18 | 1 |
Why Wei Exists
Smart Contract Precision
- Solidity (Ethereum’s language) uses integers
- Decimals would cause rounding errors
- Wei allows precise calculations
Gas Fee Calculation
- Gas prices are measured in Gwei (gigawei)
- 1 Gwei = 1,000,000,000 wei
- Example: 20 Gwei gas price = 20,000,000,000 wei
Micro-transactions
- Enables very small payments
- Important for DeFi protocols
- Prevents rounding issues
Practical Usage
When interacting with Ethereum:
- Wallets display amounts in ETH
- Smart contracts work in wei
- Gas prices shown in Gwei
- Block explorers may show both
Example Conversion
0.05 ETH = 50,000,000,000,000,000 wei
= 50,000,000 GweiWei in Daily Use
Most users never need to think about wei directly. Exchanges like Coinbase and Binance handle conversions automatically. Wei matters mainly for developers building on Ethereum.
Named After
Wei Dai created b-money, a precursor to Bitcoin, and contributed to cryptography research that influenced cryptocurrency development.
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