Figure proportions are important as they will help determine the age and character of your character for a dolls house or model scene. The average person is measured by artists and sculptors based on the proportions of the head. Most people are 7.5 times the height of their head tall. Heroic, or heroine figures, slim and tall ballet dancers are usually roughly 8 heads tall. Eight year olds are roughly 6 heads tall, babies are 4 heads tall.
You can adapt the age and appearance of your figure by giving them a larger or smaller head than normal for their height (then they may appear as an adolescent or a child or as more of a caricature).
If you are going to make a 1:12 scale dolls house doll that is 6 inches tall to represent a six foot man, in real size that man would have a head 72 inches/7.5 (number of heads to body) or 9.6 inches high. Your six inch high doll would need a head between 9/12 and 10/12 of an inch high to represent this size.If you are making a 1:24 scale female doll that represents someone 5' 4 inches tall, you will need a 64 inch/7.5 = 8.5 inch head which in 1:24 scale is 8.5 / 24 or .34 inches tall, about 1/3 of an inch high.