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Number Base Converter Tool

Convert between binary, octal, decimal, and hexadecimal. Supports negative numbers and bit width.

Last updated: 2026/10/16 Developer Feedback & bug reports
Options
Convert
Decimal DEC
Binary BIN
Octal OCT
Hexadecimal HEX
Custom
Base
About Number Bases
BINUses only 0 and 1. Used in computer processing
OCTUses digits 0-7. Used in Unix file permissions
DECUses digits 0-9. Everyday number system
HEXUses 0-9 and A-F. Used in color codes and memory addresses

To convert fractions such as 0.1 to binary or hex, use the Decimal Base Converter (repeating digits, error and steps included).

How to Use

1

Enter a value

Enter the number you want to convert. Negative numbers are also supported.

2

Auto convert

The value is automatically converted to other bases as you type.

3

Set options

Configure bit width, prefix display, and 4-digit separator.

About This Tool

A free online tool to convert between binary, octal, decimal, and hexadecimal. Includes advanced features like two's complement, bit width, and programming prefixes.

Features

  • Convert 4 bases at onceBinary, octal, decimal, and hex displayed simultaneously.
  • Negative numbers supportCorrectly convert negative numbers using two's complement.
  • Bit width selectionSpecify 8/16/32/64 bits to match programming data types.
  • Programmer-friendly displayPrefix (0b, 0o, 0x) and 4-digit separator options.

Use Cases

  • Number conversion in programming
  • CSS color code verification
  • Bit operations and two's complement
  • Unix file permission checking
  • Digital circuits and embedded development

FAQ

Can I use uppercase or lowercase for hex A-F?
Yes, both work correctly. Output is displayed in uppercase.
What is two's complement?
A method computers use to represent negative numbers. Enable signed mode to display negatives in two's complement format.
Why specify bit width?
To match programming data types like 8/16/32/64 bit integers.
What are prefixes?
Notation used in programming languages: 0b (binary), 0o (octal), 0x (hexadecimal).

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Related Guides

What Is a Number Base? Binary, Octal, and Hex Basics Made Simple Learn the basics of number bases (binary, octal, hex): why computers use binary, the 0b/0o/0x notation, how to convert to and from decimal, the relationship between bits and bytes, and why hex is used for things like color codes. Bitwise Operations Basics: AND, OR, XOR, NOT, Shifts, and Masks Explained Learn the basics of bitwise operations from scratch: the AND, OR, XOR, and NOT logic operations, left and right shifts, how to set and clear individual bits, masks and flag management, the link to powers of two, and real uses like permissions, color, and optimization. What Is Two's Complement? Representing Negatives, Invert-and-Add-One, and Ranges Learn two's complement from the ground up: how computers represent negative numbers, the invert-the-bits-and-add-one method, the role of the sign bit, overflow, and the ranges representable in 8/16/32 bits.