Results Change w/o Change of Input Data

Ok, 99 cents not expensive for a simple application. I would assume that the results would be more accurate since it is using a mathematical equasion. I put in my weight, age, height, and gender. If you leave these alone after inputing them in and press the "Calculate" button multiple times, your results will change each time. How does this make sense. Does 2+2=4 or maybe 5, no 7, waight 3! Ugh really?

takidenza about Body-Mass-Index