Ethereum Unit Converter is a free online tool that converts between wei, gwei and ether with exact integer arithmetic — type a value in any unit and the other two update instantly, with no floating-point rounding. It also estimates what a transaction costs at any gas price. Everything runs in your browser; nothing leaves the page.

Convert — type in any unit

Wei (10⁰ — the base unit)

Gwei (10⁹ wei — gas prices)

Ether (10¹⁸ wei — value)

Gas-cost calculator

Gas limit (units)

Gas price (gwei)

Sample ETH price (USD)

Cost in wei—

Cost in gwei—

Cost in ether—

Cost in USD (sample price)—

The ETH price above is a sample value you can edit — it is not a live market price. The USD figure is an estimate only.

Unit magnitudes

Unit	Wei	Used for
wei	1	The base unit — everything on-chain is counted in wei
kwei	1,000	Rarely used in practice
mwei	1,000,000	Rarely used in practice
gwei	1,000,000,000	Gas prices — the unit you see in every wallet
szabo	1,000,000,000,000	Historical; rarely used today
finney	1,000,000,000,000,000	Historical; rarely used today
ether	1,000,000,000,000,000,000	Balances and transfer values

How the units relate

Wei is the smallest unit of ether: 1 ether = 10¹⁸ wei, and 1 gwei = 10⁹ wei. On-chain, every amount is an integer number of wei — there is no such thing as half a wei.
That is why this page converts with BigInt integer math instead of floating point: a JavaScript Number can only represent integers exactly up to 2⁵³, while 1 ether is already 10¹⁸ wei. Floats would silently round your money away.
Gas is priced in gwei and paid in wei: cost = gas limit × gas price. A standard transfer uses 21,000 gas, so at 20 gwei it costs 420,000 gwei — 0.00042 ether.