Convert any amount between Ethereum's seven units. Most useful for reading gas prices in gwei and contract values in wei without counting zeros by hand.
wei
Smallest on-chain unit
1,000,000,000,000,000,000
kwei
10^3 wei
1,000,000,000,000,000
mwei
10^6 wei
1,000,000,000,000
gwei
Gas prices are quoted here
1,000,000,000
szabo
10^12 wei
1,000,000
finney
10^15 wei
1,000
ETH
10^18 wei
1
Ethereum works internally in wei, not ether. One ether is 10^18 wei, a one followed by eighteen zeros. The reason is that the EVM only handles integers: there are no decimal numbers at protocol level, so division is solved by making the base unit absurdly small. Any value you see in a contract, a log or an RPC response is expressed in wei.
Between wei and ether sit intermediate units named after figures from cryptography and computing. Kwei is 10^3 wei, mwei is 10^6, gwei is 10^9, szabo is 10^12 and finney is 10^15. In practice only two get daily use: wei, for contract values, and gwei, the unit gas fees are quoted in. When a wallet says the network is at 25 gwei, it means 25,000,000,000 wei per unit of gas.
That eighteen-order-of-magnitude spread is exactly where floating point breaks. A double-precision number only guarantees around fifteen or sixteen significant digits, so a wei value with eighteen digits can no longer be represented exactly. That is why every conversion on this page uses big integers: 1 ETH returns exactly 1000000000000000000 wei, and a thirty-digit value converts without losing a single digit.
The most common practical case is working out what a transaction costs. Multiply the gas price in gwei by the gas used, convert to ETH and multiply by the market price. A simple transfer uses 21,000 gas: at 25 gwei that is 525,000 gwei, or 0.000525 ETH. This tool handles the unit side so you do not have to count zeros.
