Hi Adele-
I'm Kevin B. Windows user like you. I do apologize for the inconvenience, let me help you sort things out.
Kindly reset your calculator app.
Go to settings > apps.
Select Calculator and click on Advanced options.
Click on the Reset button.
Once its reset check if the issue persists.
If the issue persists, you can uninstall and re install the application.
Open powershell (admin)
Copy and paste this command then hit enter:
Get-AppxPackage *windowscalculator* | Remove-AppxPackage
Once its finish go to your Microsoft Store the look for calculator.
Install the app then check it again.
Please let me know what will happen. Hope this will help and have a blessed day!
Thanks,
Kevin B.
Independent Advisor