Number Base Converter
Convert numbers between binary, hexadecimal, octal and decimal instantly with this free number base converter in your browser.
Enter a value to convert it across all bases.
Exact for very large numbers. Hex is shown uppercase. Runs in your browser.
How to use this calculator
- Pick the base your value is in (binary, octal, decimal or hex).
- Type the value to see it in all four bases at once, each with a copy button.
How it works
Each base uses a different set of digits — binary uses 0–1, octal 0–7, decimal 0–9, hex 0–9 then A–F. The value is the same number written different ways.
Conversion uses big-integer maths, so it stays exact even for long binary or hex strings well beyond a normal calculator's limit.
Worked example
255 in decimal. = 11111111 (binary), 377 (octal), FF (hex).
Common mistakes
- Entering a digit that doesn't exist in the chosen base, e.g. a '2' in a binary value or a 'G' in hex.
- Forgetting hex letters go A–F only (10–15); there's no hex 'G'.
Frequently asked questions
What do binary, octal and hex digits go up to?
Binary uses 0–1, octal 0–7, decimal 0–9, and hexadecimal 0–9 then A–F (which stand for 10–15).
Can it handle very large numbers?
Yes — it uses big-integer arithmetic, so even a 64-bit hex value converts exactly.
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Cite this tool
Zerdly. (2026). Number Base Converter. Retrieved from https://www.zerdly.com/tools/number-base-converter/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.