About this tool

Number System Conversions

Convert numbers between binary, octal, decimal, hexadecimal, and base-36 with real-time precision, supporting large integers and Unicode.

Number System Conversions shows one whole number simultaneously in binary (base 2), octal (base 8), decimal (base 10), hexadecimal (base 16) and base-36, with the 0b, 0o and 0x prefixes applied where they belong. Every card also reports the bit width, the byte count rounded up to the next whole byte, and the Unicode character at that code point when the value falls within the valid range up to U+10FFFF. Conversion runs on JavaScript BigInt rather than Number, so values past 2^53 keep every digit instead of silently losing precision.

How to use Number System Conversions

1. 1

   Open Number System Conversions on AltFTool — it loads instantly in your browser.

2. 2

   Pick the Input format — Binary, Octal, Decimal, Hexadecimal or Base-36 — and type the value into the box below it; 0b, 0o and 0x prefixes and a leading minus are accepted.

3. 3

   All five base cards recompute as you type, using BigInt so a value past 2^53 keeps every digit.

4. 4

   Each card shows the value with its 0b/0o/0x prefix plus Bits, Bytes and the Unicode character, has its own Copy, and Copy all puts all five lines on the clipboard; binary beyond 64 characters reads "Too large".

Why use Number System Conversions

• All five bases at once

  Base 2, 8, 10, 16 and 36 update together as you type, so you compare representations instead of converting one pair at a time.

• Exact past 2^53

  BigInt arithmetic means a 30-digit value converts digit-for-digit, where a normal float-backed converter starts rounding.

• Width and code point alongside

  Each card shows bit length, bytes rounded up, and the Unicode character for the value, which is usually what you actually needed next.

Common use cases

• You are setting a Unix file mode and want to see 493 as octal 755 and as the binary 111101101 that maps to the rwx bits, without switching to a shell.
• A protocol spec gives a field as a decimal constant and you need the hex literal for the header plus the bit width, to confirm it still fits in two bytes.
• You are checking which character a code point lands on — enter 8364 and read the Unicode column to confirm it is the euro sign before hardcoding it.

Frequently asked questions