Time/Numbers
Number Base Converter
Convert between binary, octal, decimal, hexadecimal, and any arbitrary (2-36) base — enter a number into any field.
Number systems are just different ways of writing the same number. Binary (base 2) is what processors use at the lowest level, hexadecimal (base 16) is a compact way to write binary data in code, and decimal is the everyday human notation.
How to use it
- Enter a number in any field (binary, octal, decimal, hexadecimal, or a custom base 2-36) — every other field updates instantly.
- For a custom base, pick any value from 2 to 36 — handy for less common systems, like base36 used in short identifiers.
- Characters invalid for the selected base (like a "2" in binary) are flagged as an input error.
Common uses
- Converting a hex color or byte value into a decimal number for calculations.
- Checking a bitmask or set of flags written in binary.
- Working with low-level code (network protocols, embedded systems) where values are often given in hex or octal.
Things to keep in mind
In hexadecimal, the letters A-F (or a-f) stand for the values 10-15 — case usually doesn't matter.
For bases above 16, digit symbols keep going further down the alphabet (G, H...) up to Z for base 36.
Article about this tool: Number systems: why binary, octal, and hexadecimal exist
Frequently asked questions
Which number systems does the converter support?
Quick access to binary, octal, decimal, and hexadecimal, plus any base from 2 to 36 — digits above 9 are represented with Latin letters A-Z.
Can I convert negative numbers and very large integers?
Yes, a "-" sign before the number is supported in every base, and there's no fixed 32/64-bit limit on the number's size — calculations use arbitrary precision.
Is data sent to a server?
No, all conversion happens instantly in your browser via JavaScript — the numbers you enter are never sent anywhere.
How is numeral-system conversion different from Base64?
These are fundamentally different things: a numeral-system converter translates the same number between positional systems (BIN/OCT/DEC/HEX), while Base64 encodes arbitrary binary data (files, images) into a text string for transmission over channels designed for text.
Why does hexadecimal use the letters A-F?
Base 16 needs 16 unique digits, but Arabic numerals only provide 10 (0-9) — so the values 10-15 use the first letters of the Latin alphabet, A-F. For bases above 16 (up to 36), letters continue further down the alphabet.