See previous calculations in Calculator on Mac
In the basic or scientific calculators, you can keep track of previous calculations and copy results from them to use in Calculator or other apps.
Go to the Calculator app
on your Mac.While in the basic or scientific calculator, do one of the following:
Choose View > Show History in the menu bar.
Press Control-Command-S.
Do any of the following:
Reload the calculation: Click the listing. The calculation appears where you left off earlier.
Copy the answer: Control-click the listing, then choose to copy the expression or result.
Tip: Whenever you calculate anything, you can choose Edit > Copy to save it to your clipboard.
Delete the calculation: Control-click the listing, then choose Delete.
Tip: Swipe left on any entry, then click 
to copy or 
to remove it.