i guess the best method is

........take a number say 1100110011

now

2^0*1=1
2^1*1=2
2^2*0=0
2^3*0=0
2^4*1=16
2^5*1=32
2^6*0=0
2^7*0=0
2^8*1=256
2^9*1=512

and add the results
1+2+16+32+256+512

thats all

good luck