The Calculator dialog allows users easy access to three prescription lens calculators on three separate tabs: ‘Intermediate/Near Lens Power’, ‘Power/Prism/Slab-Off’ and ‘Vertex Distance’. To access this dialog, go to Tools > Calculator from the main menu. You could also open the Calculator dialog by pressing [Ctrl][R] on your keyboard.

The Windows Calculator could be accessed from this dialog by clicking the Math Calculator button or by pressing [Ctrl][T] on your keyboard from anywhere in the application.