🔤 ASCII Table Reference: Decimal, Hex, Octal, Binary and HTML Codes

What is the ASCII Table?

ASCII (the American Standard Code for Information Interchange) is a character encoding that maps the numbers 0 to 127 onto letters, digits, punctuation and a set of control codes. It was first standardised in 1963 by the American Standards Association, revised in 1967 and again in 1986, and it remains the foundation of modern text. The first 128 code points of UTF-8 and Unicode are byte-for-byte identical to ASCII, so a plain ASCII file is also a valid UTF-8 file. Because every code fits in 7 bits, ASCII is compact, unambiguous and supported on essentially every computer, language and protocol in use today.

The 128 codes split into two groups. Codes 0 to 31, plus 127, are control characters: they were never meant to be printed but to control devices such as teleprinters, modems and terminals. Familiar examples are 9 (horizontal tab), 10 (line feed, the newline on Unix, Linux and macOS) and 13 (carriage return, which Windows pairs with line feed to end a line). Codes 32 to 126 are the printable characters: 32 is the space, 48 to 57 are the digits 0 to 9, 65 to 90 are the uppercase letters A to Z, and 97 to 122 are the lowercase letters a to z. Code 127 (DEL) is technically a control code even though it sits at the very end.

A few patterns make ASCII easy to reason about and to compute by hand. Uppercase and lowercase letters are exactly 32 apart, so you can switch case by adding or subtracting 32, or by flipping a single bit (bit 5, value 32). The digit characters are deliberately not equal to their numeric values: the character '0' is code 48, so to turn a digit character into the number it represents you subtract 48. The letters are laid out in order, which is why A is 0x41 and a is 0x61, and why sorting ASCII strings byte by byte happens to sort uppercase before lowercase and both after the digits.

Web developers meet ASCII in a second guise: HTML character references. Any character can be written in a web page as a numeric reference using its decimal code (for example A for A) or its hex code (A), and a handful of ASCII characters that are special in HTML have named entities instead, such as & for the ampersand (38), < for the less-than sign (60) and " for the double quote (34). The reference table below lists these so you can paste the right code into markup without guessing. Programmers also reach for ASCII through escape sequences such as \n (line feed, 10), \t (tab, 9), \r (carriage return, 13) and \0 (the null terminator, 0).

Beyond the original 128 codes lie the so called extended ASCII sets, which use the eighth bit to define codes 128 to 255. These were never part of the ASCII standard itself: they are separate code pages such as Windows-1252, IBM code page 437 and the ISO 8859 family (with ISO 8859-1, also called Latin-1, being the most common). Different code pages assign completely different characters to the same numbers, which is exactly why a document can look fine on one machine and turn into mojibake on another. If you need accented letters, currency symbols or anything outside English, the modern answer is to use Unicode and encode it as UTF-8 rather than relying on an extended ASCII page.

In short, ASCII is small, old and astonishingly durable. It defines just 128 codes, but those codes underpin source code, network protocols, file formats and almost every keyboard you will ever touch. Whether you are escaping a character for a URL, hunting down a stray control byte that broke a CSV import, or teaching how computers store text as numbers, the table below gives you the decimal, hex, octal, binary and HTML value for every code in one place.

When to use it

• Looking up the decimal, hex, octal or binary code for a character while writing or debugging code.
• Identifying a mysterious control character (such as a stray tab, null or carriage return) that is breaking a parser, CSV import or log file.
• Building escape sequences, URL-encoded strings or regular expressions that need the exact hex value of a character.
• Finding the correct HTML numeric reference or named entity (&, <, >, ") to safely place a special character in markup.
• Teaching or learning how text is represented as numbers, including the 32-apart case shift and the 48 offset on digits.
• Converting a character to its code in any base, or back again, without reaching for a separate calculator.

How to use the ASCII Table

1. Scroll the table to browse all 128 ASCII characters from 0 to 127.
2. Type a number (for example 65, 0x41, 0o101 or 1000001) or a character into the search box to filter the rows.
3. Choose which field you want to copy (character, decimal, hex, octal or binary) from the dropdown.
4. Click a row, or focus it and press Enter, to copy that field to your clipboard.
5. Use the reference tables further down for control-code names, HTML codes and the difference between ASCII and extended ASCII.

Formula & method

Worked examples

Key ASCII ranges and what they cover

Common control codes you will actually meet

HTML codes for special and common ASCII characters

Common mistakes to avoid

• Treating a digit character as its number. The character '5' is code 53, not the value 5. To get the numeric value from a digit character you subtract 48 (the code for '0'). Forgetting this is a classic off-by-48 bug.
• Confusing CR and LF. A newline is line feed (code 10) on Unix, Linux and macOS, but Windows ends lines with carriage return then line feed (codes 13 and 10). A stray CR is a frequent cause of files that look fine but break parsers, diffs and shell scripts.
• Assuming ASCII covers accented or non-English letters. ASCII only defines codes 0 to 127, so characters like the e-acute, n-tilde or pound sign are not in it. Those come from extended ASCII code pages or from Unicode. If you see odd symbols, the text is probably UTF-8 being read as plain ASCII, or one code page being read as another.
• Mixing up the case-shift direction. Uppercase codes are lower than lowercase: A is 65 and a is 97. To go from uppercase to lowercase you add 32, not subtract it. Reversing the sign turns letters into unrelated punctuation and symbols.
• Treating extended ASCII as a single fixed standard. There is no one extended ASCII table. Codes 128 to 255 mean different things in Windows-1252, code page 437 and ISO 8859-1. Relying on a specific code page in a file that may be opened elsewhere is a common source of corrupted text.
• Forgetting to escape special characters in HTML or URLs. Characters such as & (38), < (60) and the space (32) have special meaning in markup and URLs. Writing them raw can break a page or a link. Use the HTML entity (&amp;, &lt;) or the percent-encoded hex (%20 for a space) instead.

Glossary

ASCII

The American Standard Code for Information Interchange, a 7-bit encoding mapping codes 0 to 127 to characters.

Control character

A non-printing code (0 to 31 and 127) that signals an action, such as a tab, newline or bell, rather than a visible glyph.

Printable character

A code from 32 to 126 that represents a visible glyph or the space.

Hexadecimal

Base 16 notation, using digits 0 to 9 and letters A to F. ASCII codes are often shown this way, for example A as 0x41.

Octal

Base 8 notation, using digits 0 to 7. ASCII codes appear in octal in older C escape sequences and Unix tools, for example 101 for A.

Code point

The numeric value assigned to a character. In ASCII the code points run from 0 to 127.

Extended ASCII

Any 8-bit encoding that keeps ASCII for codes 0 to 127 and adds its own characters for 128 to 255, such as Windows-1252 or ISO 8859-1. Not part of the ASCII standard itself.

HTML entity

A way to write a character in HTML using a code, either a numeric reference like &#65; or a named one like &amp;, so special characters do not break the markup.

UTF-8

A Unicode encoding whose first 128 code points are identical to ASCII, so plain ASCII text is valid UTF-8. It is used by the vast majority of web pages.

Frequently asked questions