Monmint
Free tool

Hex to Decimal Converter (uint256)

Convert hexadecimal and decimal integers in both directions — exact for full uint256 values from calldata and block payloads.

Hexadecimal is base-16 and decimal is base-10. This converter turns a hex value (like 0xde0b6b3a7640000) into its decimal form (1000000000000000000) and back, using big-integer math so it stays exact for full 256-bit numbers — the size of EVM token amounts, storage slots, and calldata words.

How it works

Hexadecimal is everywhere in Ethereum and Monad tooling: transaction data, log topics, storage slots, and ABI-encoded arguments are all hex. Each hex digit encodes 4 bits, so two hex digits make one byte — which is why a 32-byte word is 64 hex characters.

Token amounts are commonly uint256, far larger than a JavaScript number can hold exactly. This converter uses native BigInt, so a value like 0xde0b6b3a7640000 converts to exactly 1000000000000000000 (1 token with 18 decimals) without losing a single digit.

The tool also reports the byte width of the value, which is handy when you need to know whether a number fits in a uint8, uint160 (an address), or a full uint256 word.

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FAQ

Common questions

What is 0x in front of a hex number?
0x is just a prefix that marks the value as hexadecimal. 0xff and ff are the same number (255); the prefix avoids ambiguity in code.
Can it convert full uint256 values?
Yes. The converter uses big-integer math, so even the largest 256-bit values convert exactly with no rounding.
How do hex digits map to bytes?
Each byte is two hex digits (4 bits each). So 20 bytes (an address) is 40 hex characters, and a 32-byte word is 64.
Why is my decimal token amount so large in hex?
Token amounts are stored in the smallest unit (wei-scale). A '1 token' value with 18 decimals is 10^18 in the raw integer, which is a long hex string.
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