This app was very useful when calculating my used phone minutes. However a few thing needs to be improved. When they are updated, Ill give 5 star 1. When the calculation screen is full, it continues calculation but you dont see what is being calculated. I had to take the total, clear screen and start over 2. C button should clear current item not all. AC button should be added to clear all. I was using <- button couple time to clear current item and C button instead of AC. 3. Screen should use a calculator skin that would make you to think this is a real calculator. People would buy it more. I bought another one before this because that was more professional looking. At the end I bought this because that was not doing what I wanted to do. 4. If you add unit price/sec or /min or /hours this can also be used for billing. I calculated my bills then I went to iPhone calculator to calculate cost of my minutes. If you had clipboard integration, I would be able to copy but I prefer calculating cost in the app directly. 5. Provide feedback link/email and update it regularly. Thanks for the app. It did the job.