Base Number Converter
Convert integers between binary, octal, decimal and hexadecimal, plus Base26, Base36 and Base62. Type in any base and all the others update instantly. Arbitrarily large numbers are handled exactly with BigInt, and 0x / 0b / 0o prefixes and _ separators can be pasted as-is.
What does the Base Number Converter do?
A number base (radix) is how many digits a positional number system uses: 2 for binary, 8 for octal, 10 for decimal, 16 for hexadecimal. This tool shows one non-negative integer in seven bases at the same time. Edit any field and the rest are rewritten, so you can go from hex to binary as easily as from decimal to hex. Numbers of any length are converted exactly in your browser.
How to use
- Type or paste a number into the field of its base, for example FF in [16] Hexadecimal. The other fields show 255, 11111111, 377 and so on.
- If you type a character that the base does not allow, the field turns red and explains why. Leaving the field restores the last valid value.
- Press the Up / Down arrow keys in any field to add or subtract 1 (the value does not go below 0).
- Uncheck Description to hide the short explanation under each field.
- Drag the handle on the left to reorder the bases.
Supported bases
| Base | Digits | 255 is written as |
|---|---|---|
| Binary (2) | 0-1 | 11111111 |
| Octal (8) | 0-7 | 377 |
| Decimal (10) | 0-9 | 255 |
| Hexadecimal (16) | 0-9, A-F | FF |
| Base26 | A-Z (A = 0, Z = 25) | JV |
| Base36 | 0-9, A-Z | 73 |
| Base62 | 0-9, A-Z, a-z | 47 |
Input rules
- Only non-negative integers are supported (no minus sign, no fractions).
- Binary, octal, decimal and hex fields accept the prefixes 0b, 0o and 0x and the digit separator _ (for example 0xFF_FF or 0b1010_0101).
- Hexadecimal, Base26 and Base36 are case-insensitive; hexadecimal is always displayed in upper case.
- Base62 is case-sensitive: A is 10 and a is 36.
Features
- Seven bases side by side, all editable
- Exact conversion of very large integers using BigInt (no 2⁵³ limit)
- Clear error messages for invalid digits
- Step the value with the arrow keys
- Your last number, field order and the Description setting are saved in this browser
FAQ
Why does Base26 not match spreadsheet column letters?
Here Base26 is a true positional system where A = 0, so Z = 25 and BA = 26. Spreadsheet columns count from A = 1 and have no zero digit (Z = 26, AA = 27), which is a different scheme.
My Base62 result differs from another tool. Why?
Base62 has no single standard alphabet. This tool uses the order 0-9, A-Z, a-z. Libraries that use 0-9, a-z, A-Z produce different strings for the same number.
Can it convert negative numbers or two's complement?
No. Negative values, fractions and fixed-width two's complement are not supported.