Carpenter's Calculator

Working with US Customary units (feet and inches) often involves measurements in fractions of an inch, and therefore mixed-number arithmetic. For example: you need to rip 6 planks at 3 5/16" width each. Your saw blade kerf is approximately 1/8". To figure out how much width you need in total, you'd do 6 * (3 5/16 + 1/8). You can do this in your head, but it's easy to make a mistake -- and if you add any more complexity, it becomes a challenge. You can do it on paper, but that's a bit cumbersome for such a simple operation. With the Carpenter's Calculator, it's easy.
Even if you're not a woodworker and uninterested in using fractions or mixed numbers, this calculator should offer you just about everything that the built-in iOS calculator offers, but with a feel closer to a traditional scientific or graphing calculator. It also stores your last 20 expressions and results, which makes it very easy to do slightly more complex calculations without needing to whip out a pencil and paper.