As an illustrator one may be asked to create a number of figures for any book assigned. In my case I needed some accurate heights for an entire range of people from infants to adults. Using the basic scientific ratios for number of heads high an individual is, I created my own "head count" chart.
For me it was easier to use the heads on characters I had created to make sure the sizes matched correctly. The chart above is for a realistic view of the figure. For other more cartoony styles the head count here will not match. I do find it helpful enough to keep it on my bulletin board next to my desk *:)
The chart above is very helpful when I have a question about height and have no model to use as a reference. Of course these characters are all standing but you can apply some of the rules to sitting or active figures with a bit of adjusting.
If you are an illustrator with a need for such a chart, please feel free to download and keep this on as a reference. You could make your own by using your character style and just the numbers posted above each character on this chart.