Binary, hex and ASCII reference

All reference tables

How the lookup reads what you type

A single letter or symbol is read as a character, so A gives 65. Digits are read as a decimal number, which means 101 is a hundred and one, not five. The one exception is a run of eight or more 0s and 1s, such as 01000001, which is read as binary because a byte written out has eight digits.

To be sure, add a prefix: 0x for hex (0x41) or 0b for binary (0b101). You can also pick Character, Decimal, Hex or Binary under the box. A value with the letters A to F and no prefix, such as 7B, is read as hex, and so are web colors like #FF8800 and code points like U+00E9.

Which table to open

• You have a letter or symbol: the ASCII table gives its code in decimal, hex and binary, and the binary alphabet lists A to Z on its own.
• You have a number up to 1023: the binary numbers chart shows it in binary, hex and octal, with a Print button for the whole chart.
• You are reading bytes or color codes: the hexadecimal table covers 00 to FF, every value one byte can hold.
• You are teaching it: the binary worksheets print with answer keys, and the binary clock gives students a binary number to read that changes every second.

Frequently asked questions

What is A in binary?

01000001. A is 65 in ASCII, and 65 is 64 + 1, so the bits for 64 and 1 are on.

What is the difference between ASCII and Unicode?

ASCII has 128 codes, 0 to 127. Unicode keeps those same 128 as its first code points and adds the letters of every other script, plus symbols and emoji. The guide to Unicode, UTF-8 and ASCII explains how each one is stored.

Why does the lookup show two bytes for é?

é is code point 233, past the end of ASCII. UTF-8 stores it as two bytes, C3 A9, which is what you see in a file or a hex dump.

Can I print these tables?

Yes. The binary numbers chart and the hexadecimal table have a Print button, and the worksheets are PDFs ready to print.