Write down the binary number:
10000001
Multiply each digit of the binary number by the corresponding power of two:
1x27 + 0x26 + 0x25 + 0x24 + 0x23 + 0x22 + 0x21 + 1
Solve the powers:
1x128 + 0x64 + 0x32 + 0x16 + 0x8 + 0x4 + 0x2 + 1x1 = 128 + 0 + 0 + 0 + 0 + 0 + 0 + 1
Add up the numbers written above:
128 + 0 + 0 + 0 + 0 + 0 + 0 + 1 = 129.
This is the decimal equivalent of the binary number 10000001.