Magic Calculator is described as 'scientific calculator that allows to write expressions in infix notation' and is an app in the Education & Reference category. There are five alternatives to Magic Calculator for a variety of platforms, including Mac, iPhone, iPad, Self-Hosted solutions and Apple Watch. The best alternative is Soulver. It's not free, so if you're looking for a free alternative, you could try NoteCalc or MyScript Calculator. Other great apps like Magic Calculator are PCalc (Paid) and "Converter" (Paid).
Soulver is a smart notepad with a built-in calculator. It gives instant answers to any calculations it finds in your text. It's a better way to work stuff out than with a traditional calculator, and a more lightweight tool for quick calculations than a spreadsheet.