How do I convert hex to decimal by hand?

Write each digit’s value (A = 10 up to F = 15), multiply it by 16 raised to its position counted from 0 at the right, and add: 1F4 = 1 × 256 + 15 × 16 + 4 = 500.

What is FF in decimal?

255, the largest two-digit hex number and the largest value of one 8-bit byte. FFFF is 65535 and FFFFFFFF is 4294967295.

What does 0x in front of a number mean?

It marks the number as hexadecimal in C, JavaScript and many other languages: 0x1A is 26. Typing 0x in the field switches the From base to hexadecimal, and 0o switches it to octal. The Copy as menu adds 0x to a hex result, in upper or lower case.

Can it convert very large hex numbers?

Yes, up to 4,096 decimal digits, with whole-number arithmetic: DEADBEEF is 3735928559 and FFFFFFFFFFFFFFFF is 18446744073709551615, every digit exact. An ordinary JavaScript number holds whole numbers exactly only up to 9,007,199,254,740,991.

How do I convert a negative hex number?

Type the minus sign: -FF is -255. The converter keeps the sign and does not use two’s complement, so FF is never read as -1. Padding to a bit width is shown for values of 0 and above.

Can I convert a list of hex values?

Yes. Open Batch and paste up to 200 lines, one value per line. Each row shows the value in decimal, hex, binary and octal, and a line that is not a valid number says why.

Hex to Decimal

Convert hex to decimal, binary or octal with exact whole-number math: FF is 255. Pads hex to 8, 16, 32 or 64 bits and converts 200 lines at once. How it works

From

From base

To base

Whole numbers only: fractions are not supported. Negative numbers keep a minus sign. One space or underscore between digit groups is accepted, and a 0x, 0o or 0b prefix switches the From base (a hex number that starts with 0B stays hexadecimal).

Decimal result

255

About the Hex to Decimal

Hex FF is 255 in decimal: F is 15, and 15 × 16 + 15 = 255. To convert hex to decimal, multiply each digit by a power of 16 (1, 16, 256, 4,096 and so on from the right) and add the results, with A to F standing for 10 to 15.

Common hex values in decimal and binary

Hex	Decimal	Binary
A	10	1010
F	15	1111
10	16	10000
64	100	1100100
7F	127	1111111
80	128	10000000
FF	255	11111111
100	256	100000000
1F4	500	111110100
3E8	1000	1111101000
400	1024	10000000000
1000	4096	1000000000000
FFFF	65535	1111111111111111

Largest values by bit width

Bits	Unsigned max (hex)	Unsigned max (decimal)	Signed max (hex)	Signed max (decimal)
8	FF	255	7F	127
16	FFFF	65535	7FFF	32767
32	FFFFFFFF	4294967295	7FFFFFFF	2147483647
64	FFFFFFFFFFFFFFFF	18446744073709551615	7FFFFFFFFFFFFFFF	9223372036854775807

Signed maximums are for two’s-complement integers, where the top bit is the sign, so 7F is the largest signed byte and 80 the first value read as negative.

Frequently asked questions

How do I convert hex to decimal by hand?: Write each digit’s value (A = 10 up to F = 15), multiply it by 16 raised to its position counted from 0 at the right, and add: 1F4 = 1 × 256 + 15 × 16 + 4 = 500.
What is FF in decimal?: 255, the largest two-digit hex number and the largest value of one 8-bit byte. FFFF is 65535 and FFFFFFFF is 4294967295.
What does 0x in front of a number mean?: It marks the number as hexadecimal in C, JavaScript and many other languages: 0x1A is 26. Typing 0x in the field switches the From base to hexadecimal, and 0o switches it to octal. The Copy as menu adds 0x to a hex result, in upper or lower case.
Can it convert very large hex numbers?: Yes, up to 4,096 decimal digits, with whole-number arithmetic: DEADBEEF is 3735928559 and FFFFFFFFFFFFFFFF is 18446744073709551615, every digit exact. An ordinary JavaScript number holds whole numbers exactly only up to 9,007,199,254,740,991.
How do I convert a negative hex number?: Type the minus sign: -FF is -255. The converter keeps the sign and does not use two’s complement, so FF is never read as -1. Padding to a bit width is shown for values of 0 and above.
Can I convert a list of hex values?: Yes. Open Batch and paste up to 200 lines, one value per line. Each row shows the value in decimal, hex, binary and octal, and a line that is not a valid number says why.

Reading hex from memory dumps and error codes

Programmers read hex in memory addresses, error codes, byte dumps and register values, and turn it into decimal to compare or count. The page opens on FF to decimal, pads a hex result to 8, 16, 32 or 64 bits as bytes, copies it with or without a 0x prefix, and converts a pasted list of up to 200 values into all four bases. For decimal to hex, set the From base to decimal: the same page converts either way.

How hex becomes decimal

Multiply each hex digit by a power of 16, counting from 0 at the right, and add: decimal = dₙ × 16ⁿ + … + d₁ × 16 + d₀, with A = 10 through F = 15.

Example: 1F4 is 1 × 256 + 15 × 16 + 4 = 500.

Each hex digit is exactly 4 bits, so two digits make one byte: FF is 255, the largest byte. The conversion uses whole-number (BigInt) arithmetic, so FFFFFFFFFFFFFFFF comes out as 18446744073709551615 with every digit; values up to 4,096 decimal digits are accepted. Typing 0x or 0o switches the From base to hex or octal; 0b switches to binary unless the field is already hex, because 0B1 is a valid hex number.

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