Well I finally got the program to test and it is pretty interesting. It calibrates the picture using the nose or eye. Then you go through several measurements by a series of mouse clicks on the normal measurement areas. They say it is accurate within 4 inches. It can be hard to get accurate on small pics or those where the nose or eye is hard to measure. It is very user friendly and I look forward to using it more in the future. I'll try and find a pic here in the forum and try and measure it.