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ASCII to Binary Converter
See the exact byte pattern behind every letter you type.
The letter A is not stored as a letter. Underneath, it is the number 65, and 65 is 01000001 — that eight-digit pattern is what actually sits in memory when you type a capital A.
A standard from 1963
ASCII, the American Standard Code for Information Interchange, was first published in 1963 and finalised through a few revisions into the version still used today. It assigns every letter, digit and common punctuation mark a number from 0 to 127, which fits in 7 bits.
Computers work in bytes of 8 bits, not 7, so a full byte is used to store each ASCII character with the top bit left at 0. That spare bit was not wasted by accident — it became the foundation for Extended ASCII and, much later, for how UTF-8 tells a single-byte ASCII character apart from a multi-byte one.
Where the numbers actually start
The ordering is not random. Digits 0 to 9 sit at 48 to 57, uppercase letters at 65 to 90, and lowercase letters at 97 to 122, each block running in alphabetical or numeric order so that comparing characters as numbers behaves the way you would expect.
Space, at 32, sits below every printable digit or letter, which is why sorting text with a naive byte comparison pushes blank entries to the top. The first 32 codes, 0 to 31, are not printable characters at all — they are control codes such as tab, line feed and carriage return, left over from an era of teletype machines.
A few characters and their binary codes
| Character | Decimal | Binary (7-bit) |
|---|---|---|
| Space | 32 | 0100000 |
| 0 | 48 | 0110000 |
| A | 65 | 1000001 |
| Z | 90 | 1011010 |
| a | 97 | 1100001 |
| z | 122 | 1111010 |
ASCII to binary questions
How many bits does one ASCII character need?
Seven bits, covering values 0 to 127, which is the entire original ASCII range. In practice each character is stored in a full 8-bit byte, with the extra bit left as 0 for plain ASCII text.
Why does A convert to 1000001?
Because the letter A was assigned decimal value 65 in the ASCII standard, and 65 in binary is 64 + 1, or 1000001. The assignment itself is simply a fixed lookup table agreed on in 1963.
Why do uppercase and lowercase letters have different codes?
A computer has no concept of a letter having two cases — it only sees numbers, so uppercase and lowercase had to be given separate, distinct codes. A is 65 and a is 97, a gap of exactly 32.
What are the codes below 32 used for?
Control codes, not printable characters — things like tab (9), line feed (10) and carriage return (13). They date back to controlling physical teletype and printer hardware rather than displaying anything on screen.
Does this tool handle characters outside basic ASCII?
Only the original 128 characters have a fixed 7-bit ASCII code. Accented letters, symbols and emoji live outside that range and are represented using Unicode encodings such as UTF-8, which use more than one byte per character.
