How to convert base 2 to base 10.

The binary ("base two") numerical system has two possible values, often represented as 0 or 1, for each place-value. In contrast, the decimal (base ten) numeral system has ten possible values (0,1,2,3,4,5,6,7,8, or 9) for each place-value. To avoid confusion while using different numeral systems, the base of each individual number may be specified by writing it as a subscript of the number. For example, the binary number 10011100 may be specified as "base two" by writing it as 100111002. The decimal number 156 may be written as 15610 and read as "one hundred fifty-six, base ten". 

The decimal number is equal to the sum of powers of 2 of the binary number's '1' digits place: