I run an older version of macOS, but it's historically been the case that Command-C copies the result of a calculation entered in Spotlight. They key is that th

I run an older version of macOS, but it's historically been the case that Command-C copies the result of a calculation entered in Spotlight. They key is that the Copy command must be performed when the calculation is not selected for the result to be copied to the Clipboard. Put another way, type the math to be performed in Spotlight, then press Command-C and the result has been copied.