Numi is a utility that comes as an alternative to using Mac's Calculator app for solving math equations. The application features a nicely-designed interface, immediately provides you with the accurate results you need, and comes without a price tag.
Besides helping you make math calculations, this program also enables you to convert between multiple measuring units. What's more, Numi is an efficient currency converter, updating its currency rates several times a day.
In my testing, the application offered me accurate results within moments. It used a very small amount of CPU resources while running in the background. Plus, you can reveal its main window by hitting a defined key combination (you can define it in the Settings menu of the app).
The only aspect that bothers me is the fact that it supports only one output format when exporting calculations to your local folders. This format is compatible only with the Numi program and has the NUMI extension.
Still, this application is one of the best and most intuitive Mac calculators I've tested on my computer. It's effective, easy-to-use, and free. So, you should give it a try if you're looking for an efficient alternative to using Mac's Calculator for solving equations.