Is there a built in calculator app for iPad

I like this one: https://apps.apple.com/ca/app/sci-pro-calculator/id684978583

iPad doesn’t have a built-in App - and many “free” calculator Apps in the App Store are monetised through advertising.

One of the very best calculators in the App Store - that happens also to be both completely free and without any advertisements whatsoever - is Sci:Pro Calculator:

https://apps.apple.com/gb/app/sci-pro-calculator/id684978583

There are also many very good "paid" calculator Apps - such as PCalc - that include additional advanced functionality and conversions:

https://apps.apple.com/gb/app/pcalc/id284666222

no, but you can find tons of free ones in app store

Siri can do simple arithmetic.