Q. How to convert Binary to Octal and Hexadecimal?

Rules for these conversions are simple. For converting binary to octal binary number is splitted in groups of three, that are then joined by place value to produce equivalent octal. For illustration binary number 1101011.00101 can be converted to Octal in below manner:

(Please note that number is unchanged even though we have added 0 to complete grouping. Also note that style of grouping before and after decimal. We count 3 numbers from right to left whereas after decimal from left to right.)

So octal number equivalent to binary number 1101011.00101 is (153.12)₈.

In the same manner by grouping 4 binary digits and finding equivalent hexadecimal digits for it can make hexadecimal conversion.  For illustration the same number would be equivalent to (6B.28)_H.

On the contrary we should conclude that hexadecimal digit can be splitted into a string of binary having 4 places whereas an octal can be splitted in string of binary having 3 place values. Figure below gives binary equivalents of octal and hexadecimal numbers. 

Figure: Binary equivalent of octal and hexadecimal digits