Numi App - Numi is a beautiful text calculator for Mac.
Integral Calculator - Calculate Integral Online and Free
Parsify Desktop - Extendable calculator for the 21st century ⚡
Rule of 3 Calculator - Apply the mathematical Rule of Three in an easier, faster and more practical way!
Soulver - Soulver is a software application that functions as a calculator that allows you type a continuous stream of information rather than having to input data into multiple cells.
WolframAlpha - WolframAlpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.