Decimal to Hex Converter

Q: Can I convert many decimal numbers at once?

Yes. Put one number per line and every line is converted, with the results lined up against the input. A line that is not a valid decimal number is left blank and reported by line number, so one typo does not stop the rest.

Q: How do you convert decimal to hex by hand?

Divide by 16 repeatedly and note the remainders, writing 10–15 as A–F; read the remainders from last to first. 300 → 18 r12 (C), 18 → 1 r2, 1 → 0 r1, so 12C.

Q: How do I convert an RGB value to hex?

Convert each channel separately and pad to two digits: rgb(255, 128, 0) is FF, 80, 00, so #FF8000. Paste the three channel values on separate lines with byte padding on to get all three at once.

Q: Why does my programming language give a different hex for big numbers?

If it goes through a double-precision float, integers above 2^53 lose their last digits before conversion. This tool uses exact arithmetic. In JavaScript, use BigInt(value).toString(16) to get the same result.

Convert decimal to hexadecimal instantly — exact at any size — with 0x prefix, byte padding and two's complement for negatives.

Decimal

Hex

Group digits Add 0x / 0b / 0o prefix Uppercase hex Pad to whole bytes

What It Does

This converter writes a decimal number in hexadecimal. It is exact for numbers of any size, including 64-bit IDs and values beyond what JavaScript can hold, and it tells you how many bytes the result occupies. Options add the 0x prefix, pad to an even number of digits, and switch between upper and lower case.

When to Use It

You need a decimal constant as a hex literal in code.
You are converting an RGB channel value (0–255) to its two-digit hex form for a colour.
You are matching a decimal error or status code against hex documentation, such as Windows HRESULTs.
You need a large database ID or Snowflake ID in hex without losing precision.

Worked Examples

255

FF — one byte, all bits set. Also the maximum value of one colour channel.

3735928559

DEADBEEF. Four bytes, so it fits a 32-bit unsigned integer.

9007199254740993

Larger than 2^53 − 1. Exact here (20000000000001), but JavaScript's Number would round it.

Features

Converts as you type

Bulk conversion one number per line

Exact for numbers of any size

Digit grouping and 0x/0b/0o prefixes

Swap direction in one click

Explains bit width and two's complement

How to Use

1. Type or paste a decimal number — or a list, one per line. 2. The hex value appears alongside, line for line. 3. Use the options to group digits or add a prefix, and the swap button to convert the other way.

Common Mistakes

Converting a number through a JavaScript Number. Above 9,007,199,254,740,991 it silently rounds, so the last digits come out wrong. This tool uses BigInt and stays exact at any size.
Forgetting that the same digits mean different values in different bases. 10 is ten in decimal, two in binary, eight in octal and sixteen in hex — always label which base a value is in.
Treating a minus sign as how a computer stores a negative number. Hardware uses two's complement, so a negative value's bit pattern looks nothing like its positive counterpart.

Frequently Asked Questions

Can I convert many decimal numbers at once?

How do you convert decimal to hex by hand?

How do I convert an RGB value to hex?

Why does my programming language give a different hex for big numbers?

Conversion runs in your browser with exact integer arithmetic. Nothing is uploaded.