A photographer's utility for calculating lens formulas.
None of these formulas are difficult to compute with a scientific calculator, but doing it by hand is slow, tedious and error-prone.
The faster you can get an answer, the faster you can get back to shooting. Or, you can take the same time to learn the answer to more questions! When you let
ƒ/Calc do the hard work, you gain an intuitive feel for what the results mean, because you can quickly try new input values to see how they affect the result.