The Metropolitan Museum in NYC has a few Greek Bronze Age helmets in beautiful condition on display that could have been worn at the siege of Troy. The startling thing is that they would probably only fit a 7th grader today. Much of the other Greek armor in their collection from that period, grieves and the like, are about the same size. They were small back then. Another thing rather interesting are the body shapes of the warriors depicted on pottery from that era. Their hamstrings are developed far out of proportion to the rest of the body. This is a clue that speed in closing for a sharp attack, or sprinting away to evade one, was one of the most important assets for the ideal Argive.
as to size — you see the same small men in medieval armor. these guys were mostly five feet tall.
Inches have only been put on in the last 100 years.