IStock Photo 1306071 © Janis Dreosti

Men and women who have grown up together and then become a couple share an unusual memory: they can remember when they were the same height. For most, it is a seesaw—rough parity when they’re young, then a growth spurt for the girl before a greater one for the boy. Though they hadn't known each other as children, one recently-engaged couple who lived that moment—Violet and Patrick, from Oakland, California—found a way to capture their fleeting time of height equality. They’ve framed their Little League trading cards together, with their freckled seven-year-old faces smiling toothily outward underneath large baseball caps. The cards list their stats, including height: Violet clocked in at 4’1,” Patrick at 4’ even (4’ is in fact the national average for boys and girls in their age range). At seven years old, Violet had a good inch on him but the moment was brief: now she’s a petite 5’6” and Patrick’s a lanky, basketball-loving 6’4.”

Height is a surprisingly important topic in society. Studies show that taller-than-average people tend to be more successful in terms of wealth, status, and in one recent study, even happiness. Personal ads are full of height requirements, especially among women looking for men.

So what may be really surprising is how little variation there is in height among the population as a whole. For men, grow an inch over 6 feet tall and you’re a statistical outlier. For women, the same holds true if you’re taller than 5’7." And the statistical fall-off at the shorter end of the scale is even more dramatic.

For example, among 30-39 year old men, the odds are 1 in 11.49 that a man will be shorter than 5’5” and 1 in 5.18 that he’ll be 6’ or taller. Overall, men tend to be shorter than 6’—the odds of this range from 1 in 1.12 (89%) to 1 in 1.36 (74%) depending on the age group. As a tall man, then, Patrick is something of an outlier: 1 in 3.77 men in their twenties are over six feet tall.

Violet, on the other hand, at 5’6,” falls into a common category: the odds a woman in her twenties is shorter than 5’7” are 1 in 1.17 (85%). Among all age groups, women tend to be shorter than 5’7,” with the odds ranging from 1 in 1.04 (96%) to 1 in 1.2 (83%). The odds a woman in her twenties is 5’10” or taller are just 1 in 83.33.

On a societal level childhood nutrition and environment have a lot of influence on a population’s height. Taller populations tend to be better fed and less diseased, and some scientists make a direct link (as they do with longevity) between trends in population height and the overall thriving of a society. But from person to person, it is our genes—as expressed in the heights of our immediate ancestors—that matter most. That’s why simple formulas such as this one or this do-it-yourself version posted by Dr. Robert H Shmerling of the Beth Israel Deaconess Medical Center will often predict height within 2-3 inches:

For men: (height of mother + height of father + 5)/2
For women: (height of mother + height of father – 5)/2