Wei, Gwei, ETH explained: what every denomination is for

Ethereum’s native token has ten named denominations from Wei to Tether (a different, larger Tether unrelated to the stablecoin). In practice three of them carry the weight: Wei (the atomic protocol unit),Gwei (the gas-pricing unit), and ETH(the user-facing unit). Knowing which one you’re looking at saves you from the recurring confusion of seeing a wallet balance like 12,000,000,000,000,000,000 and wondering whether you’re rich.

The three units that matter

Everything else (Kwei, Mwei, Szabo, Finney…) exists in documentation and not much else. You’ll never see them in a wallet.

Why Wei is the atomic unit

Ethereum smart contracts work in integer math. Floating-point doesn’t exist on-chain; division can’t produce fractions. So balances are stored as integer counts of the smallest unit. ETH has 18 decimal places of precision; the smallest unit (Wei) is 10⁻¹⁸ ETH. A wallet showing “1 ETH” is really storing the integer 1,000,000,000,000,000,000 Wei.

The 18-decimal precision is overkill for any current economic use case, but it’s built in so that sub-cent-priced tokens (or future ETH valued at $1m+) still have meaningful precision. Compare to Bitcoin, which has 8 decimals (1 BTC = 10⁸ satoshis) and is occasionally constrained by it.

Why gas is priced in Gwei

Gas prices are typically 1-200 Gwei. In ETH that’s 10⁻⁹ to 2×10⁻⁷ — too many zeros for humans to track. In Wei it’s 10⁹ to 2×10¹¹ — too many zeros in the other direction. Gwei sits in the middle and lets gas prices be expressed as small integers.

Concrete example. You send a normal ETH transfer (21,000 gas units) at a 30 Gwei gas price.

• Gas used: 21,000
• Price per gas: 30 Gwei = 30 × 10⁹ Wei
• Total Wei: 21,000 × 30 × 10⁹ = 6.3 × 10¹⁴ Wei
• In ETH: 6.3 × 10¹⁴ / 10¹⁸ = 0.00063 ETH
• At $3,000/ETH: about $1.89 in fees

Doing the same math in straight ETH or straight Wei is painful; Gwei is the unit that makes it tractable.

Why this matters when reading transactions

Etherscan shows transaction values in ETH because humans want to read them that way. The raw valuefield in the transaction is a hex string representing the Wei count. Pasting that hex into a parser, converting to decimal, dividing by 10¹⁸ gets you back to ETH.

Example value field: 0x10a741a462780000.

• As decimal Wei: 1,200,000,000,000,000,000
• Divided by 10¹⁸: 1.2 ETH

Our Wei/Gwei/ETH converter does this conversion exactly, using JavaScript BigInt so the precision survives even for very large Wei values that overflow a regular Number.

The other denominations (for completeness)

From smallest to largest:

1. Wei — 10⁻¹⁸ ETH. Atomic unit.
2. Kwei (Babbage) — 10⁻¹⁵ ETH. Effectively unused.
3. Mwei (Lovelace) — 10⁻¹² ETH. Unused.
4. Gwei (Shannon) — 10⁻⁹ ETH. Gas pricing.
5. Szabo (Microether) — 10⁻⁶ ETH. Unused.
6. Finney (Milliether) — 10⁻³ ETH. Unused.
7. ETH (Ether) — 1 ETH. Standard unit.
8. Kether (Grand) — 10³ ETH. Whale notation, mostly tongue-in-cheek.
9. Mether — 10⁶ ETH. Notional.
10. Gether / Tether — 10⁹ / 10¹² ETH. Numerically interesting only.

The named units are themed after computer-science pioneers (Babbage, Lovelace, Shannon, Szabo, Finney). They appeared in early Ethereum documentation but almost never appear in wallets, block explorers, or modern tooling.

Other EVM chains use the same denominations

Polygon (MATIC/POL), BNB Chain (BNB), Arbitrum (ETH but on L2), Optimism (ETH on L2), Base (ETH on L2), Avalanche (AVAX) — they all use the Wei-Gwei-native-token scheme. Replace “ETH” with the native token name and the math is identical. The naming “Gwei” sometimes gets reused (“30 Gwei” on Polygon means 30 × 10⁹ POL-wei, not 30 × 10⁹ ETH-wei).

The 60-second mental model

• Think in ETH for balances and prices.
• Think in Gwei for gas.
• Think in Wei only when reading raw transaction data.
• 1 ETH = 10⁹ Gwei = 10¹⁸ Wei. Convert with our Wei/Gwei/ETH calculator.

Sources: Ethereum Foundation Yellow Paper (Wood, latest revision); EIP-1559 specification; Etherscan unit glossary.

Step-by-step walkthrough: computing an EIP-1559 transaction fee

EIP-1559 split the old single “gas price” into a protocol-determined base fee (burned) plus a user-set priority fee (tip to the validator). The full computation:

fee_wei = gas_used × (base_fee_per_gas + priority_fee_per_gas)
          (capped at gas_used × max_fee_per_gas)

Concrete example. You broadcast an ERC-20 transfer (~65,000 gas) on Ethereum mainnet during moderate congestion. Network conditions:

• Base fee: 28 Gwei (≈ 28 × 10⁹ Wei per gas unit)
• Your priority fee: 2 Gwei (typical for non-urgent transfers)
• Your max fee: 50 Gwei (safety ceiling in case base fee spikes during the next block)

Effective per-gas cost: 28 + 2 = 30 Gwei = 30 × 10⁹ Wei. Total transaction fee:

• 65,000 × 30 × 10⁹ = 1.95 × 10¹⁵ Wei
• ÷ 10¹⁸ = 0.00195 ETH
• At $3,400/ETH = $6.63

Decomposing where the money goes:

• Burned (base fee × gas): 65,000 × 28 × 10⁹ = 1.82 × 10¹⁵ Wei = 0.00182 ETH → permanently removed from supply
• Validator tip (priority fee × gas): 65,000 × 2 × 10⁹ = 1.30 × 10¹⁴ Wei = 0.00013 ETH → paid to the proposer

93% of your fee burns; 7% tips the validator. This is the normal split under EIP-1559 outside congested periods. During NFT mints or major DEX events, priority fees spike to 50+ Gwei while base fees stay anchored, flipping the ratio.

Common mistakes when working with Wei and Gwei

• Using JavaScript Number for Wei arithmetic.JavaScript’s Number is a double-precision IEEE 754 float and loses precision above 2⁵³ ≈ 9.007 × 10¹⁵. 1 ETH (10¹⁸ Wei) overflows this by 100×. Always use BigInt or a library like ethers.js’s parseUnits() / formatUnits(). See our BigInt glossary entry for the precision math.
• Confusing decimal places between tokens. ETH has 18 decimals; USDC has 6; WBTC has 8. A smart-contract function that expects a token amount as an integer in the token’s native units will silently misbehave if you pass “Wei-style” 18-decimal scaling to a 6-decimal token. Always checkdecimals() on the ERC-20 contract.
• Quoting gas in Wei.Gas prices are conventionally quoted in Gwei (10⁻⁹ ETH). A bot or monitoring tool that reports “current gas: 28 billion” (Wei) is technically correct but essentially unusable; convert to Gwei before display.
• Forgetting L2 native-token math. Arbitrum, Optimism, and Base use ETH as the gas token with the same Wei/Gwei conventions, but Polygon (POL), BNB Chain (BNB), and Avalanche (AVAX) have their own native tokens with the same 18-decimal scaling but different USD value. The arithmetic looks the same; the dollar conversion isn’t.
• Reading the value field as a decimal string. Etherscan and most JSON-RPC responses serialise value as a hex string prefixed 0x. Parsing it with parseInt() works only for tiny amounts; for any real ETH amount use BigInt("0x10a741a462780000") and then divide.

When the Wei / Gwei / ETH model does NOT apply

• Bitcoin and pre-EVM chains.Bitcoin uses 8-decimal satoshis (1 BTC = 10⁸ sats), not 18-decimal subunits. Solana uses 9-decimal lamports. Cardano uses 6-decimal lovelace. Don’t reuse Ethereum tooling assumptions on these chains.
• ERC-20 tokens with non-standard decimals. Most ERC-20s use 18 decimals like ETH, but USDC and USDT use 6, WBTC uses 8, and some older or experimental tokens use 0 (integer-only) or 24+ decimals for very-small-value applications. Always read decimals() from the contract interface; never assume.
• Rebasing and elastic-supply tokens. AMPL, OHM, and similar protocols modify balances algorithmically. The on-chain Wei-equivalent count changes between blocks without any transfer. Standard wallet UIs handle this; custom integrations need to re-read balances on every block, not cache.

For deeper protocol background, the EIP-1559 specification defines the fee market mechanics, and the Ethereum Yellow Paper formalises Wei as the protocol atomic unit. For interactive conversion the Wei/Gwei/ETH converter uses BigInt under the hood so the precision survives even pathological inputs.

Reading Etherscan like a pro

Etherscan presents the same transaction data three different ways. Knowing which view to use:

• Default view. Shows ETH amounts in standard 18-decimal format. Best for: quick sanity checks, casual lookups.
• “Click to see more” expanded view. Reveals gas used, gas price in Gwei, base fee, max fee, priority fee, transaction status. Best for: debugging failed transactions, computing effective fees.
• “See more details” raw JSON. Shows the underlying RLP-encoded transaction data including the value field as hex Wei. Best for: programmatic parsing, audit trails, forensic on-chain analysis.

The discrepancy that sometimes confuses new users: Etherscan’s “Value” column shows the transfer amount, not the fee. A transaction can show “0 ETH value” and still have cost real ETH in fees (typical for contract interactions like a token approval or a Uniswap swap, where ETH itself isn’t moved but gas is paid in ETH).

Quick conversion reference

Memorise these factors and almost every Wei/Gwei/ETH question becomes mental arithmetic:

Typical magnitudes for the things you read on chain:

• Gas price (mainnet, calm): 5-30 Gwei
• Gas price (mainnet, congested): 80-300 Gwei
• Gas price (L2 Arbitrum/Optimism/Base): 0.01-1 Gwei
• Simple ETH transfer: 21,000 gas units
• ERC-20 transfer: 50,000-70,000 gas units
• Uniswap swap: 130,000-200,000 gas units
• NFT mint: 150,000-400,000 gas units

Multiplying the gas-unit cost by the Gwei price gives you the Wei fee. Divide by 10⁹ to get Gwei, by 10¹⁸ to get ETH, then multiply by the current ETH price for the dollar value. Four steps, none of which need a calculator if the magnitudes are familiar.