This free online binary to decimal converter instantly translates any binary number (made up of only 0s and 1s) into its decimal equivalent. Enter a binary value below to see the converted result right away.
How to Use the Binary to Decimal Converter
Type a binary number (only digits 0 and 1) into the "Enter Binary Number" field.
Click "Convert to Decimal" to see the equivalent decimal value.
If you enter an invalid character, correct the input and convert again.
How Binary Place Values Work
In decimal, each position is worth ten times the one to its right. In binary, each position is worth two times the one to its right. Reading from the rightmost digit, the places are worth 1, 2, 4, 8, 16, 32 and so on. To convert, add up the place values of every position that holds a 1, and ignore the positions that hold a 0.
The converter checks that the input contains only 0 and 1, then reads it as a base-2 number and displays the base-10 result. It treats the input as an unsigned whole number.
Worked Example: 101101
Binary digit
1
0
1
1
0
1
Place value
32
16
8
4
2
1
Contribution
32
0
8
4
0
1
Adding the contributions: 32 + 8 + 4 + 1 = 45, which is what the converter shows for 101101.
A quicker mental method is doubling. Start at 0 and, for each digit from left to right, double the running total and add the digit. For 101101: 1, then 2, 5, 11, 22 and finally 45. This avoids having to write out the place values for long numbers.
Useful Binary Values to Recognise
Binary
Decimal
Why it matters
1111
15
Largest value in 4 bits (one hex digit)
11111111
255
Largest value in one byte; each part of an IPv4 address and each RGB colour channel ranges from 0 to 255
100000000
256
Number of different values one byte can hold
10000000000
1024
2 to the power 10, the base of KiB, MiB and GiB
sixteen 1s
65535
Largest 16-bit value, also the highest network port number
A binary number made of n ones always equals 2 to the power n, minus 1. That is why 8 ones give 255 and 16 ones give 65,535.
Limitations to Keep in Mind
Signed numbers: the converter reads 11001010 as 202. If the byte is a signed value stored in two's complement, its meaning is 202 − 256 = −54. Subtract 2 to the power of the bit width yourself whenever the leftmost bit is 1 and the value is meant to be signed.
Very long inputs: results are exact up to 53 binary digits. Beyond that, JavaScript numbers lose precision, so the last few decimal digits may be rounded.
Fractions: binary points such as 1101.101 are not accepted. Convert the whole part here and add the fraction by hand: the first place after the point is worth 0.5, then 0.25, 0.125 and so on.
Spaces and prefixes: remove spaces used to group bits, and remove a leading 0b if you copied the value from code.
Frequently Asked Questions
The tool validates that your input contains only 0s and 1s, then parses it as a base-2 number, converting it to its base-10 (decimal) equivalent.
Only the digits 0 and 1 are allowed. Any other character, including spaces or letters, is treated as invalid.
Not directly. Every input is treated as unsigned, so 11111111 gives 255. If the bits are an 8-bit two's complement value, subtract 256 from the result when the first bit is 1, which turns 255 into −1. Use 65,536 for 16-bit values.
Up to 53 binary digits the answer is exact. Longer inputs still convert, but the result can be rounded because browsers store numbers in a format with 53 bits of precision. For example, 54 ones should be 18014398509481983 but display as 18014398509481984.
Convert the part before the point with this tool: 1101 is 13. Then add the fractional places, which are worth 0.5, 0.25, 0.125 and so on. For .101 that is 0.5 + 0.125 = 0.625, so 1101.101 equals 13.625.