You can enter the values using your keyboard as well as the on-screen keyboard. Read: How to use the Graphing Calculator in Windows 11/10 How do you use a Calculator to convert?

You can use QuickPath on ‌iPad‌, too. However, note that it's only available on the floating keyboard that's revealed when you pinch inward on the full-width virtual keyboard in iPadOS.

I use a Natural Ergonomic Keyboard 4000 and have always had the mouse and keyboard app installed to disable the stupid keys in the middle of it. Calculator opens in the foreground for me.