baseunits

An exact token unit converter: wei, gwei, lamports, sats, or any number of decimals.

Use it: https://khalydmaina.github.io/baseunits/

Why another converter

Because the obvious way to do this is wrong. In JavaScript:

8.2 * 1e9    // 8199999999.999999   (should be 8200000000 lamports)
1.1 * 1e18   // 1100000000000000100 (should be 1100000000000000000 wei)

Floats cannot hold token amounts. baseunits does everything with whole numbers (BigInt), so the answer is always exact, however many digits it has.

It also refuses to round. 0.0000001 USDC does not exist, because USDC only has 6 decimal places, so you get an error instead of a silently wrong number.

What it does

• Converts both ways: type in any box and the others follow.
• Presets for ETH (wei, gwei), BTC, SOL, USDC, USDT, SUI, APT, TON, NEAR, ATOM, DOT, TRX, XRP and ADA, plus any custom number of decimals up to 36.
• Hex in and out, for reading calldata and logs.
• Accepts what people actually paste: 1,500,000.25, 1_000_000, 1e18.
• Warns when an amount no longer fits in a u64 (Solana, Sui, Aptos) or a uint256.
• Shows the matching parseUnits and formatUnits calls for viem and ethers.
• Keeps the token and amount in the link, so https://khalydmaina.github.io/baseunits/#usdc/1500000 opens on 1.5 USDC.

It is two static files, index.html and units.js. Nothing is sent anywhere, and it works offline once loaded.

Use the maths in your own code

units.js has no dependencies and works in Node and in the browser:

const Units = require("./units.js");

Units.parseAmount("8.2", 9);          // 8200000000n
Units.formatAmount(1500000n, 6);      // "1.5"
Units.parseAmount("0.0000001", 6);    // throws: only has 6 decimal places

Run it locally

python3 -m http.server      # then open http://localhost:8000
node --test tests/units.test.js   # unit tests

Notes

• USDC and USDT are shown with 6 decimals, which is right on Ethereum, Solana, Tron and most chains. On BNB Chain they have 18: use Custom for that.
• Amounts cannot be negative.

License

MIT