Acqualia has Soulver Notepad Calculator (iTunes Link) for the iPhone, iPod Touch, and iPad in the iTunes App Store for 99-cents (regularly $3.99) for a limited time.

Soulver is the ultimate app for doing quick calculations and figuring stuff out on the iPhone & iPad. It’s a far more elegant way to work with numbers than a traditional calculator.

With Soulver, you write out your entire problem and you see your answer as you type. If you make a mistake, you don’t have to start again, you can edit your expression like in a text editor.

You can do calculations over multiple lines, and change any of them. You can use words alongside your numbers so they make sense which it’s great for comparing different scenarios.

Soulver is great for adding things up, and doing quick percentages. Soulver will also save your work for you when you’re done, and sync it using iCloud or Dropbox.

Once you try Soulver, you’ll never want to go back to a simulated physical calculator.