start from least significant digit and multiply each digit of binary number by 2^(n){where n=0,1,2,3,4.....}
and add the number calculated. The number obtained after addition is the equivalent decimal number.
ex.- for 10101111
1*(2^7)+0*(2^6)+1*(2^5)+0*(2^4)+1*(2^3)+1*(2^2)+1*(2^1)+1*(2^0)
= 175