PCalc

A fully featured scientific calculator with support for hexadecimal, octal and binary calculations, as well as an RPN mode, parentheses, programmable functions, and an extensive set of unit conversions.

PCalc is the granddaddy of all calculator apps. If it's not Soulver, I turn to PCalc. There is a version for iOS, iPadOS, tvOS, and watchOS, and another one for macOS.

www.pcalc.com