how binary octets convert to decimal

Here is how binary octets convert to decimal:
The right most bit, or least significant bit, of an octet will hold a value of 20. The bit just to the left of that will hold a value of 21. This continues until the left-most bit, or most significant bit, which will hold a value of 27. So if all binary bits are a one, the decimal equivalent would be 255 as shown here:

1 1 1 1 1 1 1 1
128 64 32 16 8 4 2 1 (128+64+32+16+8+4+2+1=255)
Here is a sample octet conversion when not all of the bits are set to 1. 0 1 0 0 0 0 0 1 0 64 0 0 0 0 0 1 (0+64+0+0+0+0+0+1=65)
And this is sample shows an IP address represented in both binary and decimal.
10. 1. 23. 19 (decimal) 00001010.00000001.00010111.00010011 (binary)
These octets are broken down to provide an addressing scheme that can accommodate large and small networks. There are five different classes of networks, A to E. This document focuses on addressing classes A to C, since classes D and E are reserved and discussion of them is beyond the scope of this document.