Capital letters A to Z
| Letter | ASCII code | Binary |
|---|---|---|
| A | 65 | 01000001 |
| B | 66 | 01000010 |
| C | 67 | 01000011 |
| D | 68 | 01000100 |
| E | 69 | 01000101 |
| F | 70 | 01000110 |
| G | 71 | 01000111 |
| H | 72 | 01001000 |
| I | 73 | 01001001 |
| J | 74 | 01001010 |
| K | 75 | 01001011 |
| L | 76 | 01001100 |
| M | 77 | 01001101 |
| N | 78 | 01001110 |
| O | 79 | 01001111 |
| P | 80 | 01010000 |
| Q | 81 | 01010001 |
| R | 82 | 01010010 |
| S | 83 | 01010011 |
| T | 84 | 01010100 |
| U | 85 | 01010101 |
| V | 86 | 01010110 |
| W | 87 | 01010111 |
| X | 88 | 01011000 |
| Y | 89 | 01011001 |
| Z | 90 | 01011010 |
Small letters a to z
| Letter | ASCII code | Binary |
|---|---|---|
| a | 97 | 01100001 |
| b | 98 | 01100010 |
| c | 99 | 01100011 |
| d | 100 | 01100100 |
| e | 101 | 01100101 |
| f | 102 | 01100110 |
| g | 103 | 01100111 |
| h | 104 | 01101000 |
| i | 105 | 01101001 |
| j | 106 | 01101010 |
| k | 107 | 01101011 |
| l | 108 | 01101100 |
| m | 109 | 01101101 |
| n | 110 | 01101110 |
| o | 111 | 01101111 |
| p | 112 | 01110000 |
| q | 113 | 01110001 |
| r | 114 | 01110010 |
| s | 115 | 01110011 |
| t | 116 | 01110100 |
| u | 117 | 01110101 |
| v | 118 | 01110110 |
| w | 119 | 01110111 |
| x | 120 | 01111000 |
| y | 121 | 01111001 |
| z | 122 | 01111010 |
Capital and small letters differ in one bit
Compare A, 01000001, with a, 01100001. The only change is the third bit from the left, which is worth 32. The same is true for every pair, because each small letter’s code is exactly 32 more than its capital.[2]
- Text
- Aa
- Binary
- 01000001 01100001
| Letter | ASCII code | Binary |
|---|---|---|
| A | 65 | 01000001 |
| a | 97 | 01100001 |
- 65 + 32 = 97, so small a comes 32 codes after capital A.
- Flipping that one bit switches any letter between capital and small.
Patterns that help you spot letters
- Starts with 010
- Codes 64 to 95: the capital letters A to Z, plus a few symbols placed around them.
- Starts with 011
- Codes 96 to 127: the small letters a to z, plus a few symbols and DEL.
- Ends in 00001
- The first letter of each set: A is 01000001 and a is 01100001.
- Ends in 11010
- The last letter of each set: Z is 01011010 and z is 01111010.
Questions about the binary alphabet
How many bits is one letter?
Eight. ASCII letters fit in seven bits, and computers store them in an 8-bit byte with the top bit set to 0.
Is there a binary alphabet for other languages?
Letters outside English, such as ñ or ö, are not in ASCII. In UTF-8 each of them takes two bytes, so they are not single bytes like the letters above.
Sources, last checked October 12, 2026
- Glossary of Unicode Terms (Unicode Consortium)
The American Standard Code for Information Interchange, a 7-bit coded character set for information interchange.
- RFC 20: ASCII format for Network Interchange (IETF, 1969)
The standard 7-bit character representation, with b7 the high-order bit and b1 the low-order bit, is shown below: