How do I reinstall calculator app on my iPhone

Use App Library to search the Calculator app, see -> Organize the Home Screen and App Library on your iPhone

Organize the Home Screen and App Library on your iPhone - Apple Support           

• If you have find the Calculator app, tap & hold on the app, then drag to the Home screen & drop it.

Hi! You can reinstall the Calculator app from the App Store:

1. Open Settings
2. Tap ‘Search’
3. Type “Calculator” in the field that says “Games, Apps, Stories and More”
4. Reinstall the one that has Apple listed as the developer

Have a nice day!

I want to reinstall my calculator app

Colbrook wrote:

I want to reinstall my calculator app

Follow the directions in the post above marked "Apple recommended".