Hi,
This sounds like an interesting project, and a good use of the iPhone!
So we have 2 input fields (presumably with some kind of validation on the user input), then the calculations from your spreadsheet, to produce a result.
I develop apps for iPhone/iPod Touch/iPad running iOS 9 and 8, using Xcode and Swift (so iOS-only, no Android, just to be clear).
You can see some examples of my work, and client reviews of my completed projects, on my Freelancer profile page (under "portfolio").
It would be useful if I could have a look at your spreadsheet, to get an idea of the complexity of the calculations which are used in your process. If you'd like to respond to this message, we can discuss things further, before you make your decision on awarding the project.
Best Regards,
- Rob Dixon.