Drawing a well-proportioned human body freehand requires a bit of training. Practice regularly: You will be amazed at how fast you progress. To your pencils!
French has an expression "Quel canon" ["What a canon!]said about attractive looking people. This expression comes from Ancient Greece. Canon in both English and French refers to the norm for calculating the proportions of the "perfect man." Of course, you don't need to follow it to the letter, but it is a good guide.
The Vitruvean Man: This is the "perfect man" drawn by Leonardo da Vinci in 1490 in his still famous sketch. By drawing the body human as geometric forms, he showed the proportional relationships between its various limbs.
Nowadays, more simply, we use head height as our unity of reference. Total body height is equal to eight times head height.
Drawing a man using the following equivalences for each part of the human body:
To get an idea closer to reality, do the partitioning yourself:
For children, proportions are different from adults. The younger the child, the more room its head takes.
For a 6 year old child, body height equals 6 times its head height. For a 12 year old child, it is 7 times.