Boys' Fitting Room
Leave it to Aunt Hill to introduce an easy size guide that works for all body sizes and shapes.
It's not likely you will find the exact height and weight on this chart. Like The Price is Right, you want to find the closest measurement to that of the young gentleman without going over the number on the chart.
Start with What you Know
This chart takes age, height, and weight into account. Knowing the height and weight of the young gentleman will provide the best data for ordering the right size. Locate the colours of the ranges that best describe his height and weight. Locate the point on the chart where these meet. This colour (either his height, weight, or both) is the young gentleman's size for all articles of clothing throughout Aunt Hill.
For the convenience of those that don't have the young gentleman near enough to weigh and measure him (and if asking for these details might seem creepy), the size chart includes the age at which children usually hit these physical growth benchmarks.
He Will Grow
We haven't actually managed to shrink any kids at all yet so, when in doubt order a size up.
A Note About Numbers
This chart corresponds with Canadian national averages, as reported by national and international organizations including the Canadian Paediatric Society, Canadian Paediatric Endocrine Group, College of Family Physicians of Canada, Community Health Nurses of Canada, Dietitians of Canada, US National Center for Health Statistics, and the World Health Organization.
These numbers are not ideals. They represent the height and weight of the largest "average boy" in most Canadian classrooms that are grouped by age. This doesn't mean that the sizes are big, rather that most boys of that age will not grow out of clothing that size too quickly.
Naturally, some boys are much bigger or smaller than their peers. For this reason, it's preferable to rely on better data like height and/or weight than only age. A photo (especially one in which there are adults) may help determine how "average" he is.