Hey, This is Jess. I was a Sales Representative at Nike, and during my job, I had to go through many types of Apparel, Shoes, Belts, Hats, Cap and Accessories. I would often get customers' measurements from them and then decide which size they should buy based on the measurement.
I found that the size charts were not available online for many brands. And also, the measurement tools didn't really work for some people. So I decided to create my own website where I could provide people with sizing information in one place.