Here is an app that can calculate 27 different formulas useful in financial transactions.
This latest version of the app has added a numeric keypad (with nice large keys) for data entry, as an alternative to the 2 modes of data entry in the original version: (1) dragging your finger up or down the screen to increase or decrease the default value of an input parameter, (2) tapping on a blank space on the screen for the same purpose.
The 27 formulas can be divided into 5 categories: (1) interest functions which range from simple interest to mortgage payments to bond price to yield a specified interest when the stated rate of the bond (frequently called coupon rate) is specified, (2) notes and payments, (3) profit and loss (including internal rate of return), (4) inventory valuation, (5) depreciation.
This app can only calculate the 27 specified formulas, but it is free.
If several thousand people download it and give me favorable reviews, I will do an enhanced app (for which I will charge a few dollars) that will allow the user to specify his/her own formulas, which may incorporate one or more of these 27 hard coded formulas.
A virtual numeric keypad has been added for those who would rather enter data the old-fashioned way, instead of dragging or tapping.