What is the Number Base Converter?
Type a number in any field (binary, octal, decimal, hexadecimal or a custom base) and all the others update instantly. It is handy for reading memory addresses, colour codes, file permissions like 755, bit flags, network masks and low-level protocol data.
Conversions use arbitrary-precision integers, so even 100-digit numbers convert exactly, without the rounding you get in a normal calculator. For negative numbers, the two’s complement bit patterns used by computers are shown for 8, 16, 32 and 64 bits.
How to use it
- Type a number into any of the fields.
- Read the same value in every other base.
- Set a custom base (2–36) if you need one.
- Turn on grouping to split long numbers into readable chunks.
Example
Decimal 255
Binary 1111 1111 · Octal 377 · Hex FF
Features
- All common bases. Binary, octal, decimal and hexadecimal side by side.
- Any base 2–36. A custom field for base 3, 5, 32, 36 or any other base.
- Exact for huge numbers. Arbitrary-precision arithmetic, so no digits are lost.
- Prefixes understood. Paste 0x1F, 0b1010 or 0o755; underscores and spaces are ignored.
- Two’s complement. 8-, 16-, 32- and 64-bit patterns for negative numbers.
- Readable grouping. Binary and hex in groups of four, decimal with thousands separators.
Frequently asked questions
How do I convert binary to decimal?
Each binary digit is worth twice the one to its right: 1, 2, 4, 8, 16 and so on. Add the values where there is a 1. For example 1011 is 8 + 2 + 1 = 11. Type the binary number into the Binary field to see it instantly.
Why is hexadecimal used so much?
Each hex digit is exactly four binary digits, so hex is a compact way to write bytes: FF is 1111 1111. It is used for colours (#18488B), memory addresses, hashes and MAC addresses.
What is two’s complement?
The way computers store negative integers: invert all bits of the positive number and add one. In 8 bits, −1 is 1111 1111. It is shown for 8, 16, 32 and 64 bits when the number fits.
Can it convert fractions?
No, only whole numbers. Fractions often have no exact representation in other bases (0.1 in binary repeats forever).
Is anything sent to a server?
No. Everything is calculated in your browser.
Last updated · Free, no sign-up, runs in your browser.