ANSI X3.4, seven bit
ASCII Table Reference
The 128 character encoding that maps the numbers 0 to 127 to letters, digits, symbols, and control codes.
At a glance
Key factsStandard
Code points
128, from 0 to 127
Letter A
Decimal 65, hex 0x41
Unicode
First 128 points identical
Where it comes from
ASCII was standardized by the American National Standards Institute as X3.4 in the 1960s. It fits in seven bits and defines 128 code points: control codes below 32 and at 127, the space at 32, and printable characters in between. The printable range is reproduced exactly in Unicode, so every ASCII file is already valid UTF-8 without any conversion.
How to use it
The layout is deliberate. Digits run contiguously from 48 to 57, so subtracting 48 from a digit gives its value. Capital letters run 65 to 90 and lower case 97 to 122, a gap of exactly 32, a single bit, which is why case folding was cheap on early hardware. Use the table to convert a character to its code point, decode a hex dump, or spot an invisible control character breaking a parser.
This page is a standing summary. For the interactive tool and the full tables, open the ascii table page. The data here is compiled from ASCII, defined by ANSI X3.4 and mirrored in the printable range of Unicode.