About

Every character transmitted across a network or stored on disk resolves to a numeric code point. The American Standard Code for Information Interchange (ASCII) maps 128 characters (indices 0 - 127) to decimal integers. Extended ASCII expands this to 256 values (0 - 255). Misinterpreting these mappings corrupts protocol headers, breaks serial communication, and produces garbled file output. This tool performs bidirectional conversion between ASCII text and its decimal representation, handling control characters (codes 0 - 31), printable characters (32 - 126), and extended range (128 - 255). Results approximate standard ASCII/ISO-8859-1 encoding. Characters outside the 0 - 255 range (Unicode) will produce code points beyond the ASCII table.

Formulas

The conversion from a character to its decimal code point uses the mapping function defined by the ASCII standard.

charCode(c) → d ∈ {0, 1, ..., 255}

Where c is the input character and d is its decimal code point. The reverse mapping reconstructs the character from a decimal value.

fromCode(d) → c, where 0 ≤ d ≤ 65535

For a string of n characters, the full conversion produces a sequence of n decimal values.

S = c₁c₂...c_n → [d₁, d₂, ..., d_n]

Where d_i = charCode(c_i) for each index i from 1 to n. Standard ASCII covers codes 0 - 127. Extended ASCII (ISO-8859-1) covers 128 - 255. JavaScript's charCodeAt returns the UTF-16 code unit, which aligns with ASCII for values within the 0 - 127 range.

Reference Data

Dec	Char	Description	Dec	Char	Description
0	NUL	Null	64	@	At sign
7	BEL	Bell / Alert	65	A	Uppercase A
8	BS	Backspace	66	B	Uppercase B
9	HT	Horizontal Tab	90	Z	Uppercase Z
10	LF	Line Feed (\n)	97	a	Lowercase a
13	CR	Carriage Return (\r)	98	b	Lowercase b
27	ESC	Escape	122	z	Lowercase z
32	SP	Space	48	0	Digit zero
33	!	Exclamation mark	49	1	Digit one
34	"	Double quote	57	9	Digit nine
35	#	Hash / Number sign	127	DEL	Delete
36	$	Dollar sign	128	Ç	Extended: C cedilla
37	%	Percent sign	169	©	Extended: Copyright
40	(	Left parenthesis	174	®	Extended: Registered
41	)	Right parenthesis	176	°	Extended: Degree
42	*	Asterisk	177	±	Extended: Plus-minus
43	+	Plus sign	181	µ	Extended: Micro
44	,	Comma	188	¼	Extended: One quarter
45	-	Hyphen / Minus	189	½	Extended: One half
46	.	Period / Full stop	190	¾	Extended: Three quarters
47	/	Forward slash	215	×	Extended: Multiplication
58	:	Colon	247	÷	Extended: Division
59	;	Semicolon	255	ÿ	Extended: y diaeresis
61	=	Equals sign	91	[	Left square bracket
62	>	Greater-than sign	92	\	Backslash
63	?	Question mark	93	]	Right square bracket

Frequently Asked Questions

The tool uses JavaScript's charCodeAt() which returns UTF-16 code units. For characters in the extended ASCII range (128 - 255), the decimal values align with ISO-8859-1 encoding. Characters beyond code point 255 (e.g., emoji, CJK characters) will return their full Unicode code point, which is outside the ASCII specification. The tool flags these as non-ASCII.

Control characters such as NUL (0), TAB (9), LF (10), and CR (13) are non-printable. When converting decimal back to ASCII, these characters are rendered using their standard abbreviations (e.g., [NUL], [TAB], [LF]) so you can identify them visually. The actual character is still stored internally for accurate copy-to-clipboard operations.

The converter accepts space-separated, comma-separated, or mixed delimiters. For example, 72 101 108 and 72,101,108 both produce the same result. The parser strips extra whitespace and empty entries. Invalid tokens (non-numeric or out-of-range values) are highlighted individually.

Unix/Linux systems use LF (Line Feed, decimal 10) as the line terminator. Windows uses CR+LF (Carriage Return + Line Feed, decimals 13 10). Classic Mac OS used CR alone (13). When pasting text from different sources, the tool preserves the exact byte sequence. If you see consecutive 13 10 pairs, the source uses Windows-style line endings.

This tool focuses on the ASCII↔Decimal conversion pair. However, the output panel displays each character's decimal value, which can be mentally converted: divide by 16 for hex, divide by 8 for octal. For example, the letter "A" is decimal 65, which equals 41 in hexadecimal and 101 in octal.

The tool caps input at 100000 characters to prevent browser memory issues. For typical use cases (protocol debugging, encoding verification, data inspection), this is more than sufficient. Processing is synchronous and completes in under 50ms for inputs up to 10000 characters.