Number Base Converter
Convert a number between binary, octal, decimal, hexadecimal, and any base from 2 to 36, right in your browser. Type in any field and the rest update live, with full precision for big numbers. Free, no signup, nothing uploaded.
How to use the number base converter
Type a Number
Enter your value in whichever field matches its base, binary, octal, decimal, or hexadecimal.
See Every Base at Once
The other fields update live as you type, so you see the same number in all bases side by side.
Use a Custom Base
Set the custom base to anything from 2 to 36 to convert into and out of less common bases, then copy any result.
One Number, Every Base
The same value looks completely different depending on the base. The decimal number 255 is 11111111 in binary and ff in hexadecimal, and switching between them in your head is slow and easy to get wrong, especially once the numbers get long.
This converter shows all of them together. Type a value in any field, in whatever base it happens to be, and the binary, octal, decimal, and hexadecimal versions fill in at once. A custom field handles any base from 2 to 36 for the less common cases.
It keeps full precision, so even very large numbers convert without losing a digit, and it flags input that is not valid for the base instead of silently producing the wrong answer. Because it runs in the browser, you can convert values from real code or hardware without sending them anywhere.
Why Use Our Number Base Converter?
All Bases at Once
Binary, octal, decimal, and hexadecimal sit side by side and update together, so you never convert one step at a time.
Any Base 2 to 36
A custom field converts to and from any base from 2 up to 36, using digits 0-9 and a-z.
Big-Number Precision
Large values keep every digit, with no rounding or loss that you get from normal number limits.
Catches Bad Input
Type a digit that is not valid for a base, like a 2 in binary, and the field flags it instead of guessing.
One-Click Copy
Copy any value with a single click, ready to paste into your code or a calculator.
Runs in Your Browser
Every conversion happens on your device. Nothing is uploaded, logged, or stored.
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Frequently Asked Questions
Common questions about converting number bases.
What bases can it convert?
It handles binary (base 2), octal (base 8), decimal (base 10), and hexadecimal (base 16) in fixed fields, plus a custom field for any base from 2 to 36 using digits 0-9 and the letters a to z.
Does it handle very large numbers?
Yes. It uses big-integer math, so numbers with many digits convert exactly, without the rounding you would get from ordinary number handling.
Why is a field marked red?
That means the value you typed has a digit that does not belong to that base, like the digit 2 in a binary field or the letter g in hexadecimal. Remove the invalid digit and it converts again.
Is hexadecimal shown in upper or lower case?
Hexadecimal and the custom bases use lowercase letters, so ff rather than FF. The value means the same either way, and you can uppercase it after copying if you need to.
Can it convert negative numbers?
Yes. Put a minus sign in front of the number in any field and the negative value is converted across all the bases.
Is this number base converter free?
Yes, it is completely free with no signup and no limits. Everything runs in your browser, so your numbers stay on your device.