web3 / uint256 converter

Paste any value — a decimal number, a 0x hex blob, or plain text — and get every representation you need for a contract call. These conversions happen in your browser; no data is sent or stored.

Input

read as

try

hex minimal, byte-aligned: —
decimal the uint256 value: —
utf-8 text, trailing 0x00 padding ignored: —
uint256 32 bytes, left-padded — how a number is ABI-encoded: —
bytes32 32 bytes, right-padded — how a short string is ABI-encoded: —
ether value ÷ 10¹⁸: —
gwei value ÷ 10⁹: —

Why

uint256 / web3 conversion for Ethereum, useful for:

manual contract and web3 interaction,
NFT minting and other uint256 arguments,
reading raw storage slots or call results from a block explorer,
turning a short string into a bytes32 parameter,
sanity-checking wei amounts before signing a transaction.

What each row means

Row	Meaning
`hex`	The minimal byte-aligned hex form. Text becomes its utf-8 bytes, numbers become big-endian hex.
`decimal`	The value read as one big-endian unsigned integer — what a contract sees as a `uint256`.
`utf-8`	The bytes decoded as text. Trailing `0x00` padding is ignored; invalid sequences are reported instead of mangled.
`uint256`	Padded to 32 bytes on the left, which is how a number is ABI-encoded.
`bytes32`	Padded to 32 bytes on the right, which is how a short string is ABI-encoded.
`ether` / `gwei`	The number divided by 10¹⁸ and 10⁹, for wei amounts.

How the input is detected

Anything starting with 0x is read as hex bytes, a plain run of digits (optionally negative, _ and spaces allowed) is read as a decimal number, and everything else is read as utf-8 text. Ambiguous input like dead or 123 can be forced with the read as selector.

Negative numbers are shown as their two's complement, because that is how int256 is encoded on-chain. Values wider than 256 bits are flagged rather than silently truncated.

Privacy

The converter is plain JavaScript running locally on native BigInt arithmetic. There is no backend, no analytics and no third-party script — the page works offline once loaded.

Need the background instead? See what uint256 means in Ethereum. The original conversion idea comes from web3-type-converter.