How do I convert decimal to binary?

Divide by 2 again and again and read the remainders from last to first: 10 ÷ 2 = 5 r 0, 5 ÷ 2 = 2 r 1, 2 ÷ 2 = 1 r 0, 1 ÷ 2 = 0 r 1, so 10 is 1010.

How do I convert binary to hexadecimal?

Split the binary digits into groups of four from the right and replace each group with one hex digit: 1111 0000 is F0, which is 240. The converter accepts the space between groups and can print binary output in 4-bit groups.

What is octal used for?

Mostly Unix file permissions, where each octal digit holds three bits: 755 in octal is 111101101 in binary and 493 in decimal.

How are negative numbers shown?

With a minus sign: -10 is -1010 in binary, -12 in octal and -A in hexadecimal. Two’s complement is not offered.

Can it convert fractions such as 0.5?

No. A decimal point or comma gets a message that fractions are not supported; only whole numbers are converted.

Can I type 0x, 0b or lowercase hex?

Yes, when the prefix matches the From base: 0xff with From set to hexadecimal gives 255, and 0b1010 with binary gives 10. With From set to decimal, 0x1F is rejected because x is not a decimal digit. Hex letters can be upper or lower case; the output uses capitals. One space or underscore between digit groups is accepted, so 1111_0000 in binary gives F0, but two spaces in a row give an error. Values are converted exactly up to 4,096 decimal digits. To get the prefix in the output, tick Show the 0b, 0o or 0x prefix: 255 then shows as 0b11111111, 0o377 and 0xFF.

Number Base Converter

Convert a whole number between binary, octal, decimal and hexadecimal and see all four at once: 255 is 11111111, 377 and FF. How it works

From

From base

To base

Group binary output in 4-bit groupsShow the 0b, 0o or 0x prefix

Whole numbers only: fractions are not supported. Negative numbers are shown with a minus sign (for example -101), not in two's complement. Digits that do not belong to the chosen base are reported by name.

Binary result

11111111

The same value in all four bases

Decimal (base 10)
255
Binary (base 2)
11111111
Hexadecimal (base 16)
FF
Octal (base 8)
377

Reference: 0 to 16

The numbers 0 to 16 in decimal, binary, octal and hexadecimal
Decimal	Binary	Octal	Hex
0	0	0	0
1	1	1	1
2	10	2	2
3	11	3	3
4	100	4	4
5	101	5	5
6	110	6	6
7	111	7	7
8	1000	10	8
9	1001	11	9
10	1010	12	A
11	1011	13	B
12	1100	14	C
13	1101	15	D
14	1110	16	E
15	1111	17	F
16	10000	20	10

About the Number Base Converter

255 in decimal is 11111111 in binary, 377 in octal and FF in hexadecimal. The number base converter shows a whole number in all four bases at once; each digit counts a power of its base, so 377 in octal is 3 × 64 + 7 × 8 + 7 = 255.

The same numbers in four bases

Decimal	Binary	Octal	Hexadecimal
10	1010	12	A
100	1100100	144	64
255	11111111	377	FF
493	111101101	755	1ED
1000	1111101000	1750	3E8
-10	-1010	-12	-A

Negative numbers keep a minus sign in every base.

Powers of two in four bases

Power	Decimal	Octal	Hexadecimal	Binary digits
2⁴	16	20	10	5
2⁸	256	400	100	9
2¹⁰	1024	2000	400	11
2¹⁶	65536	200000	10000	17
2³²	4294967296	40000000000	100000000	33
2⁵³	9007199254740992	400000000000000000	20000000000000	54
2⁶⁴	18446744073709551616	2000000000000000000000	10000000000000000	65

In binary a power of two is 1 followed by zeros. 2⁵³ is where ordinary JavaScript numbers stop holding every whole number; this converter uses BigInt and stays exact up to 4,096 decimal digits.

Frequently asked questions

How do I convert decimal to binary?: Divide by 2 again and again and read the remainders from last to first: 10 ÷ 2 = 5 r 0, 5 ÷ 2 = 2 r 1, 2 ÷ 2 = 1 r 0, 1 ÷ 2 = 0 r 1, so 10 is 1010.
How do I convert binary to hexadecimal?: Split the binary digits into groups of four from the right and replace each group with one hex digit: 1111 0000 is F0, which is 240. The converter accepts the space between groups and can print binary output in 4-bit groups.
What is octal used for?: Mostly Unix file permissions, where each octal digit holds three bits: 755 in octal is 111101101 in binary and 493 in decimal.
How are negative numbers shown?: With a minus sign: -10 is -1010 in binary, -12 in octal and -A in hexadecimal. Two’s complement is not offered.
Can it convert fractions such as 0.5?: No. A decimal point or comma gets a message that fractions are not supported; only whole numbers are converted.
Can I type 0x, 0b or lowercase hex?: Yes, when the prefix matches the From base: 0xff with From set to hexadecimal gives 255, and 0b1010 with binary gives 10. With From set to decimal, 0x1F is rejected because x is not a decimal digit. Hex letters can be upper or lower case; the output uses capitals. One space or underscore between digit groups is accepted, so 1111_0000 in binary gives F0, but two spaces in a row give an error. Values are converted exactly up to 4,096 decimal digits. To get the prefix in the output, tick Show the 0b, 0o or 0x prefix: 255 then shows as 0b11111111, 0o377 and 0xFF.

Reading one value in every base

The From and To boxes do one conversion, but the list under them shows the value in all four bases at the same time, so one paste answers every direction. Type the Unix permission 755 as octal and the list shows 111101101, 493 and 1ED: the binary shows which of the nine read, write and execute bits are set. Type a hex byte such as F0 and the binary 11110000 shows the high four bits on. With 4-bit grouping ticked, each group of four binary digits lines up with one hex digit.

Supported bases

Converts whole numbers between binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16), and lists the typed value in all four at once, each with a copy button. Other bases are not offered. A digit d in position n, counting from 0 at the right, is worth d × baseⁿ.

Example: decimal 255 is 11111111 in binary, 377 in octal and FF in hexadecimal.

The value is converted with exact integer arithmetic, so values of up to 4,096 decimal digits (about 13,600 binary digits) come out without rounding. One space or underscore between groups of digits is accepted, so grouped binary output pastes back as input. A 0b, 0o or 0x prefix that matches the source base is accepted. Tick Show the 0b, 0o or 0x prefix to write it on the output too: 255 becomes 0b11111111, 0o377 and 0xFF, and -255 becomes -0xFF, with the sign first as source code writes it. Decimal output never has a prefix. Negative numbers keep a minus sign and are not shown in two's complement, fractions are not supported, and binary output can be split into 4-bit groups.

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