Soulver is a notepad calculator. You type out your problems, and Soulver shows you the answer in parallel as you type (no equals required):
You can work things out over multiple lines, and edit previous lines at any time.
A running total of all your lines is displayed under the answers.
Soulver doesn't mind if you use words alongside your numbers, so they make more sense to you.
This can be helpful when doing budgets, or adding things up:
There's lots of other ways Soulver can help you work things out, including doing percentages, unit & currency conversions.