With Calculator Keyboard custom keyboard you can access the calculator from anywhere without switching between apps! It works within all apps!
How many times have you felt frustrated over being forced to switch between apps just to calculate something? With Calculator Keyboard, you can access the calculator by just switching keyboards! You can also add calculator keyboard as an extension to the notification center.
If you want to use only the extension or only the keyboard, you can do that too.
Add the keyboard by going to Settings->General->Keyboards->Add keyboard
This keyboard does NOT record keystrokes or send data over the internet.
The "allow access" option is only needed when changing background color and for using copy text to clipboard function.