What Is the Binary Alphabet?
In everyday searches, binary alphabet often means a chart showing how letters such as A, B, a, and b are represented as binary character codes. That is the meaning of the reference tool on this page: English letters mapped through ASCII to 8-bit binary values.
There is also a stricter computer-science meaning. In formal languages and information theory, a binary alphabet can mean the two-symbol set {0, 1}. That concept describes the symbols available to a binary string; it does not itself define a code for English letters.
For letter lookups, an encoding such as ASCII provides the missing mapping from a character to a number. Binary is then one way to write that number.
Binary Alphabet A–Z
The reference above covers all 26 uppercase letters and 26 lowercase letters. Each row shows four forms of the same character code:
- Letter — the actual English character.
- ASCII Decimal — the character’s numeric ASCII value.
- Binary — that value written as an 8-bit binary byte.
- Hex — the same value written in hexadecimal.
For example, uppercase A is decimal 65, binary 01000001, and hex 41. Uppercase Z is decimal 90, binary 01011010, and hex 5A.
If you need punctuation, digits, control characters, or the full 0–127 range, use the complete ASCII table. This page intentionally stays focused on letters A–Z and a–z.
Uppercase vs Lowercase Binary Letters
Uppercase and lowercase letters do not share the same ASCII or binary value. ASCII assigns them separate numeric ranges:
| Letter | ASCII Decimal | 8-bit Binary | Hex |
|---|---|---|---|
A |
65 | 01000001 |
41 |
Z |
90 | 01011010 |
5A |
a |
97 | 01100001 |
61 |
z |
122 | 01111010 |
7A |
That difference matters when encoding text. A and a may look related to a reader, but a computer receives different byte values for them.
How Letters Become Binary
For basic English ASCII letters, the conversion can be summarized as:
Character → ASCII code → byte value → binary
Take uppercase H as an example. ASCII assigns H the decimal value 72. Decimal 72 written in base 2 is 1001000; when displayed as a full 8-bit byte, it becomes 01001000.
The same process works for every English letter in the table. For complete text or sentences, the Text to Binary converter performs the conversion for each character and produces copyable byte groups.
Example: HELLO in Binary
HELLO converts one character at a time:
| Character | ASCII Decimal | Binary |
|---|---|---|
H |
72 | 01001000 |
E |
69 | 01000101 |
L |
76 | 01001100 |
L |
76 | 01001100 |
O |
79 | 01001111 |
Combined, the result is:
01001000 01000101 01001100 01001100 01001111
If you already have binary bytes and want to recover readable characters, use the Binary to Text converter.
Binary Alphabet vs ASCII
Binary by itself does not contain an English alphabet. It is a base-2 number system using the digits 0 and 1. The letter-to-number relationship comes from a character encoding.
ASCII defines the numeric codes for basic English letters, digits, punctuation, and control characters. Once a letter has an ASCII number, that number can be represented in decimal, hexadecimal, octal, or binary without changing the underlying character code.
This is why a binary code chart for letters is really an ASCII letter chart shown in base 2. For more background on how binary numbers work, see Binary Basics: 0 and 1.
ASCII vs UTF-8 for English Letters
UTF-8 is compatible with ASCII for code values 0–127. That means the English letters A–Z and a–z use the same single-byte values in both ASCII and UTF-8. For example, A is the byte 01000001 in either case.
Characters outside standard ASCII can require two, three, or four UTF-8 bytes, so this A–Z chart should not be treated as a complete Unicode reference. For the distinction between the character set and the encoding, read ASCII vs Unicode vs UTF-8.