Calculator

iPads have never shipped with a calculator app.

There are literally hundreds of free and paid calculator apps for iPad/iPadOS in the iOS App Store.

Should be able to find a calculator app that you like and meets your needs there.

Best of Luck to You!

Nope, you need to download one from the App Store,

You may use the iPad’s Search bar to do simple calculations.

Use Search on your iPhone, iPad, or iPod touch - Apple Support

No but the iPhone does :)

Suggest feedback to Apple: https://www.apple.com/feedback/

May be try Microsoft Math Solver? https://math.microsoft.com/en/