[gregoriol]

On macOS, there is the excellent Numi app

Sadly I haven't found any equivalent for iOS (iPhone and iPad): it would definitely get my money!

[filleokus]

Numi would be my favourite of all these kind of calculators on macOS, if it wasn't for the lack of unit calculations[0], e.g density = 2 kg / 3 l, mass = 10 dm^3 * density

[0]: Not sure of the actual term in English

[asimpletune]

I think the term in English is dimensional analysis