Decimal to Hex

About Decimal to Hex

Decimal to Hex turns ordinary numbers into hexadecimal. Paste one, or a whole column from a spreadsheet or a database. Every line is converted, exact to the last digit, even for 64-bit IDs that other converters round.

Turn on Prefix to get 0x in front, or switch to lower case for code that wants 0xff. Set Signed to write negative numbers the way a computer stores them.

The same tool, set up for other bases: Hex to Decimal, Binary to Decimal, Decimal to Binary, Hex to Binary, Binary to Hex, Number Base Converter.

How to use it

1. Paste decimal numbers, one per line, or load a file. Commas, tabs and semicolons also split a line, so a column from a spreadsheet works.
2. Check From and To, next to Convert. On a phone they are under More.
3. Press Convert (Alt C). Results shows every number in the To base and in decimal, hex, binary and octal. Output shows only the answers, line for line, for Copy and Download.
4. Open Steps to see the math for one number, the way you would do it on paper.
5. Swap (Alt S) puts the answers in the editor and turns From and To around, so you can check the way back.
6. In Options: Signed for two's complement, Groups for 1111 0000 or 4,294,967,295, Prefix for 0x, 0b or 0o, and how many digits a fraction gets.

How to convert decimal to hex by hand

Divide by 16 and keep the remainder each time. When the answer is 0, read the remainders from the bottom up:

2014 ÷ 16 = 125   remainder 14 → E
 125 ÷ 16 =   7   remainder 13 → D
   7 ÷ 16 =   0   remainder  7 → 7

Read from the bottom up: 7DE

Check the answer the other way: 7 × 256 + 13 × 16 + 14 = 2014. Swap does this for a whole list in one press.

Decimal to hex chart

Dec  Hex     Dec  Hex     Dec   Hex      Dec      Hex
  0  0        16  10      100   64       1,000    3E8
  9  9        32  20      127   7F       4,096    1000
 10  A        50  32      128   80      10,000    2710
 11  B        64  40      200   C8      65,535    FFFF
 15  F        99  63      255   FF   1,000,000    F4240

Negative numbers and two's complement

Set Signed to write a negative number the way a computer stores it. At 16-bit, -1 is FFFF and -255 is FF01.

How two's complement works, with a table and the method by hand.

Exact for big numbers

Database IDs often pass 2^53. This tool uses BigInt, so 9007199254740993 gives 20000000000001. A converter built on JavaScript numbers rounds it first and gives 20000000000000.

Why other converters round past 2^53.

Common errors

Scientific notation

A spreadsheet or a log can write one million as 1e6. The tool reads only plain digits, so it tells you what to do.

1e6
Scientific notation is not read. Write 1e6 in full, with all its digits.

1000000

A hex letter in a decimal number

Decimal has no letters. A number such as 1A is hex, so open Hex to Decimal for it, or set From to Hex.

1A
A is not a decimal digit. Decimal uses 0 to 9. Remove the A,
or set From to base 11 or more.

The letter O for a zero

Typed by hand, a capital O and a zero look the same. The tool names the letter, so you know what to type.

12O4
The letter O is not a digit. Type the digit 0 (zero) in its place.

1204

Two numbers on one line

A space can group the digits of a big number, as in 4 294 967 295. When the groups are not all 3 digits, the tool still reads one number, 2811 in hex here, but marks the line, because it may be a list.

10 25 7
Read as one number, 10257. If these are separate numbers, put each on
its own line or split them with commas.

10, 25, 7

A number too big for its bits

With Signed set to a width, every number must fit in it. The message gives the range.

300 (Signed: 8-bit)
300 does not fit in signed 8 bits. Signed 8-bit numbers go from -128 to 127.
Pick a wider Signed setting, or set it to Off.

Decimal to hex in code and Excel

JavaScript  (255).toString(16)             // "ff"
            9007199254740993n.toString(16) // exact past 2^53
Python      hex(255)                       # '0xff'
            format(255, "X")               # 'FF'
C           printf("%02X", 9)              // 09, two digits
Java        Integer.toHexString(255)       // "ff"
Excel       =DEC2HEX(255)                  → FF
            =DEC2HEX(9, 2)                 → 09

DEC2HEX works from -549,755,813,888 to 549,755,813,887. A negative number comes back as 10 hex digits in two's complement: =DEC2HEX(-1) is FFFFFFFFFF. In Java, Integer.toHexString(-1) gives the 32-bit form, ffffffff.