I would be willing to measure my kids feet in such a way, but if I were going to the trouble of breaking out a sheet of paper to do so, I wouldn't use an app. I

I would be willing to measure my kids feet in such a way, but if I were going to the trouble of breaking out a sheet of paper to do so, I wouldn't use an app. I'd just measure the feet and do the math myself. The math is the easy part. But most people may not do that, as it involves looking up the conversion formula if you don't have it memorized.