starting with the least significant bit you multiply it by base 2 to the power zero then do the same to each of the subsequent bit while increasing the power by one to each bit then add the sum
I.e 1x2(power4) + 1x2(power3) + 0x2(power2) + 0x2(power1) + 1x2(power0) .this gives you 16+8+0+0+1 which is 25
First you write the binary number down from right to left and just above the binary numbers you write the power of two,making sure each number corresponds by its power of two.
16 8 4 2 1
1 1 0 0 1
move through each digit of the binary number i.e 1 corresponds with 1 so write 1, 2 corresponds with 0 so write 0 ,write its corresponding power of two below the binary digit
16 8 4 2 1
1 1 0 0 1
16 8 0 0 1
So to find the decimal equivalent of the binary number 11001 you sum up the numbers written below the binary number,16+8+0+0+1=25. So the binary number 11001 to decimal is 25.
1x2 ( 2 with the power 4 ) add 1x2 ( 2 with the power 3 ) add 0x2 ( 2 with the power 2 ) add 0x2 ( 2 with the power 1) add 0x2 ( 2 with the power 0 ) : This will be; 16 add 8 add 0 add 0 add 1, givving the answer 25. Thus the binary number 1101 to decimal is 25