Unicode / ASCII Simulator

See how characters are stored as numbers in ASCII, UTF-8 and UTF-16, with an interactive ASCII table.

Type some text

Every character is stored as a number (its code). The character set decides which number.

Text (try letters, symbols, accents and emoji)

ASCII only has 128 characters (codes 0–127): English letters, digits, punctuation and control codes. é 😀 cannot be stored in ASCII, so Unicode is needed.

Character	Denary code	Unicode code point	Binary stored	Bits
H	72	U+0048	1001000	7 (8 stored)
i	105	U+0069	1101001	7 (8 stored)
!	33	U+0021	0100001	7 (8 stored)
␣ (space)	32	U+0020	0100000	7 (8 stored)
c	99	U+0063	1100011	7 (8 stored)
a	97	U+0061	1100001	7 (8 stored)
f	102	U+0066	1100110	7 (8 stored)
é	233	U+00E9	not in ASCII	—
␣ (space)	32	U+0020	0100000	7 (8 stored)
😀	128512	U+1F600	not in ASCII	—

—

ASCII (7-bit)

bits

—

Extended ASCII (8-bit)

bits

112

UTF-8

bits, 1–4 bytes per character

176

UTF-16

bits, 2 or 4 bytes

320

UTF-32

bits, always 4 bytes

ASCII table (printable characters 32–126)

Click a character to see its code.

Character "A"

Denary

Hexadecimal

01000001

Lower case "a" is 97: exactly 32 more. Only bit 5 changes (01000001 → 01100001).

Codes are consecutive: if "A" is 65, then "C" is 67. Unicode keeps the same codes as ASCII for its first 128 characters.

About This Simulation

This Unicode and ASCII simulator shows how text is stored as numbers. Type any text to see each character's code in denary, hexadecimal and binary, and how many bits it needs in ASCII, UTF-8, UTF-16 and UTF-32. An interactive ASCII table shows the patterns between codes.

Features

Character-by-character table of codes for your own text
ASCII, UTF-8 and UTF-16 binary encodings
Total storage compared across ASCII, extended ASCII, UTF-8, UTF-16 and UTF-32
Warnings for characters that ASCII cannot store
Clickable ASCII table with upper/lower case and digit patterns

Topics covered

Character Sets
ASCII
Extended ASCII
Unicode
UTF-8 and UTF-16
Binary Representation of Text

Explanation

A character set is a list of characters with a unique number (code) for each one. ASCII uses 7 bits for 128 characters: English letters, digits, punctuation and control codes. Unicode gives a code to over a million characters, covering every writing system and emoji, and is stored using encodings such as UTF-8 and UTF-16.

How it works

Each character is looked up in the character set to get its code, e.g. 'A' = 65.
The code is stored in binary: 65 = 1000001 in 7-bit ASCII.
Codes are in order, so 'B' = 66 and 'a' = 97. Upper and lower case differ by exactly 32.
Digit characters are not their values: '0' is 48, so subtract 48 to get the number.
UTF-8 uses 1 byte for ASCII characters and 2–4 bytes for others, so English text stays small while any character can be stored.

Why it matters

Character sets are on the IGCSE and AS Level syllabuses, and understanding encodings is essential when handling files, web pages and databases. Many bugs ('garbled' text) come from reading text with the wrong encoding.

Frequently Asked Questions

What is the difference between ASCII and Unicode?

ASCII has 128 characters stored in 7 bits and only covers English. Unicode has codes for over a million characters from all languages, and its first 128 codes are the same as ASCII.

Why does Unicode use more storage?

It needs more bits per character to represent far more characters. UTF-8 reduces this by using only 1 byte for common ASCII characters.

What is extended ASCII?

An 8-bit version of ASCII with 256 characters. The extra 128 codes hold symbols and accented letters, but they vary between systems.

What is the ASCII code for 'A' and 'a'?

'A' is 65 (1000001) and 'a' is 97 (1100001). They differ by 32.

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