How to Use an ASCII Table and an ASCII Code Converter

Updated

Use an ASCII table when you need to look up the numeric code behind a character (or the character behind a code), and use an ASCII code converter when you need to translate a whole string or a code value in one step. ASCII.co.uk lists both tools on its homepage: the ASCII Table and the ASCII Code Converter sit under the "ASCII Tools" heading, alongside an ASCII Text Generator, ASCII Symbols, and URL Encoding.

What an ASCII table actually maps

An ASCII table is a lookup grid with two columns that matter most: the character and its decimal (and usually hexadecimal) code. Each printable character — letters, digits, punctuation — has exactly one code point, and control characters occupy the low range.

Character Decimal Hex Notes
A 65 41 Uppercase letters start at 65
a 97 61 Lowercase letters start at 97
0 48 30 Digit characters, not the number 0
space 32 20 Often the first printable code
! 33 21 Punctuation follows space

Two facts explain most confusion. First, the uppercase and lowercase blocks are separate, so A and a differ by 32. Second, the digit character 0 has code 48 — it is a symbol, not a numeric value. If you are checking a code and the number looks "off by 48," you are probably comparing a digit's character code with the number itself.

Reading the table in either direction

To go from character to code, find the character in the table and read across to the decimal column. To go from code to character, scan the decimal column and read back to the character. For anything longer than a single character, the table becomes slow — that is where the converter helps.

What an ASCII code converter does

A converter automates the lookup and handles strings. On ASCII.co.uk the tool is listed as the "ASCII Code Converter." In general, converters support these directions:

  • Text to codes — type a word or sentence and get the decimal or hex values for each character.
  • Codes to text — paste a sequence of numbers and get the readable string back.
  • Base switching — move between decimal, hexadecimal, and sometimes binary representations of the same codes.

The input is the text or number sequence; the action is choosing the direction and base; the expected result is the translated string or code list. If the output looks like garbage, check three things before anything else: whether the input was read as decimal or hex, whether spaces between codes were included or stripped, and whether the text contains characters outside the basic ASCII range (accented letters, curly quotes, emoji), which will not map to a single ASCII code.

A concrete example

Suppose you need to verify how a form field stores the word Hi!. Running it through a text-to-codes conversion should return 72, 105, 33 in decimal (48, 69, 21 in hex). If your result differs, the input likely picked up a trailing space (32) or a newline. This is the everyday use of a converter: confirming exactly which bytes a string produces.

Where these tools fit in real work

  • Programming and debugging — checking why a comparison fails because one side holds the character '0' (48) and the other holds the number 0.
  • Text processing — finding non-printing characters such as tab (9) or newline (10) that break parsing or formatting.
  • Encoding checks — confirming that a string is plain ASCII before sending it through a system that rejects other characters.
  • Teaching and documentation — showing the code behind a character when explaining how text is stored.

For quick single-character lookups, the table is faster and needs no input handling. For strings, mixed bases, or repeated checks, the converter saves time and reduces transcription errors.

Finding the tools on ASCII.co.uk

The homepage groups its resources by purpose. Under ASCII Tools you will find the ASCII Code Converter, ASCII Table, ASCII Symbols, and URL Encoding; under ASCII Art Galleries are the art collections and the ASCII Text Generator; and a Site Info section links to "What Is ASCII?" and a status page. Start at the ASCII Table for reference lookups and the ASCII Code Converter for string conversions. The site describes itself as "the place for all things textual," so the table and converter are entry points rather than the whole offering — the art galleries and text generator are separate tools for a different task.