When I entered my data and pressed "Calculate" absolutely nothing happened. No ouput of any sort appeared. Now, I am running 10.2 at the moment, but honestly, on a program as simple as this, I don't see how the different OS version could really make a difference. It's not like you're making calls to Panther-specific libraries or something. Anyway, two things: first, it needs to work, but second, I'd like to see the ability to use American Standard units as well as metric. I know metric is the way of the future and all, but some of us aren't used to it yet.