IP Subnet Calculator is a Widgets software developed by The Eldon Waldo. After our trial and test, the software is proved to be official, secure and free. Here is the official description for IP Subnet Calculator:

Edit By BS Editor: Finally, an IP Subnet Calculator. I ran out of patience waiting for someone to write one, so here you go. Minimises to a nice little bar, supports traditional and CIDR notation and generally goes about its business of calculating subnet information. Use the mouse, tab or full STOPS to switch between fields and HOLD ctrl or the apple key when clicking the small bar to MOVE the window around. When in full mode you can click anywhere in the window space to move the window normally. The colour is customisable to suit your mood.