Developer conversion tools
Binary Converter
Convert between binary, decimal, hexadecimal, octal, ASCII, and signed integer representations with instant validation.
The calculator runs in your browser and keeps entered values local to the page.
よくある質問
2進数・16進数・8進数の違いは何ですか？▾
2進数（binary）は0と1のみ使う基数2の表現で、コンピュータの基本。8進数（octal）は0〜7を使う基数8。16進数（hexadecimal）は0〜9とA〜Fを使う基数16で、メモリアドレスやカラーコードによく使われます。
負の数はどうやって表現しますか？▾
このツールは符号なし整数の変換に対応しています。負の数の2進数表現には2の補数（two's complement）が一般的に使われますが、ビット幅によって結果が変わるため注意が必要です。
CSSのカラーコードを10進数に変換できますか？▾
はい。CSSカラーコード（例：#FF5733）はRGB各チャンネルが16進数2桁で表現されています。FF→255、57→87、33→51のように各2桁を16進数として変換できます。
ASCII Quick Reference
| Char | Dec | Hex | Binary | Char | Dec | Hex | Binary |
|---|---|---|---|---|---|---|---|
| Space | 32 | 20 | 00100000 | ! | 33 | 21 | 00100001 |
| 0 | 48 | 30 | 00110000 | 9 | 57 | 39 | 00111001 |
| A | 65 | 41 | 01000001 | Z | 90 | 5A | 01011010 |
| a | 97 | 61 | 01100001 | z | 122 | 7A | 01111010 |
| \n | 10 | A | 00001010 | \t | 9 | 9 | 00001001 |
| @ | 64 | 40 | 01000000 | # | 35 | 23 | 00100011 |
| $ | 36 | 24 | 00100100 | % | 37 | 25 | 00100101 |
| & | 38 | 26 | 00100110 | * | 42 | 2A | 00101010 |
Base conversion
Move between base 2, base 8, base 10, and base 16 without manual arithmetic.
Signed integers
Check negative values with two's complement bit patterns.
ASCII helper
Convert text and character codes while debugging binary payloads.
Number Base Reference
Binary
Binary uses digits 0 and 1. Each position represents a power of two, which maps directly to bits in memory and protocols.
Hexadecimal
Hex uses digits 0-9 and A-F. One hex digit represents four bits, so it is compact for byte values and memory addresses.
Octal
Octal uses digits 0-7 and still appears in Unix permissions, where modes such as 755 map to read, write, and execute flags.
Validation
Invalid digits are rejected for the selected base, so decimal-only, hex-only, and binary-only inputs stay clear.
FAQ
Which number bases are supported?
The converter supports binary, decimal, hexadecimal, octal, ASCII text, and two's complement display for negative integers.
Does the conversion happen locally?
Yes. Values are converted in your browser and are not sent to a server.
What is two's complement?
Two's complement is the standard binary representation for signed integers. It makes addition and subtraction work consistently for negative values.
Can I use this for programming and debugging?
Yes. It is useful for bit masks, color values, file permissions, protocol debugging, and checking base conversions while coding.