I have many construction master calculators that have served me well over the years. This app is a perfect replication of their physical calculators for a fraction of the cost. One client meeting when you do not have to say, "my calculator is in the truck" and this app pays for itself. $20.00 is 4 times more than I have ever paid for an app but in this case it was a serious bargain! Perfect app without a single glitch so far.