I measured my kids using just a ruler and they're all happy with the results. I also measured myself using a mirror, ruler, and a phone camera (so the measureme

I measured my kids using just a ruler and they're all happy with the results. I also measured myself using a mirror, ruler, and a phone camera (so the measurement couldn't be skewed by eye movement) and my results also turned out great. However, I can understand why it would be easy to measure incorrectly, since the ruler is never very close to the eyes.