Keybind

Open Calculator is bound to C by default. Change it under Options → Controls → Key Binds → Craftulator.

The key opens the calculator if one is:

1. in your main hand,
2. in your off hand, or
3. worn in a Curios or Trinkets slot.

A calculator anywhere else in your inventory does not count. Right clicking with the calculator in hand always works too, whatever the keybind is.

TIP

C is not bound to anything in vanilla. If another mod also uses it, the conflict shows in red in the Controls menu. Rebind one of them.