you must multiply each digit by a power of 2.
power for right-most digit is 0 and from right to left powers increase by 1.
10011 = 1 × [tex] 2^{4} [/tex] + 0 × [tex] 2^{3} [/tex] + 0 × [tex] 2^{2} [/tex] + 1 × [tex] 2^{1} [/tex] + 1 × [tex] 2^{0} [/tex] =
16 + 0 + 0 + 2 + 1 = 19
