I accidentally deleted the Calculator app how can I redownload it again?

The calculator application in macOS is on the read-only System volume in macOS Catalina and later. It cannot be deleted as no user privileges exist to do so.

If you were referring to, and should have stated, Apple's calculator on i/Pad/OS 10 or later beginning with an iPhone 5S or iPad Air (or later models) then you have the link.

Sorry, but I am not sure I understand what you are saying. What do you mean by “original calculate”?

If I understand you correctly, you are trying to say, "accidentally deleted the original Calculator app ", so here you go and download it. --> Calculator --> Apple

Click ▶︎ Calculator App.

Have fun! 👋🏼😉