I use this app pretty much every time I make a trade for position sizing and risk management. I have an Excel spreadsheet that does the same thing but usually I use this app instead. There is an issue with the Fixed fractional position risk calculator. If you have a very low risk trade it will calculate a buy value greater than your portfolio value field. If that happens you can just lower the Risk % field to limit the size of the trade.
DT844 about Trade Optimizer: Stock Position Sizing Calc Calculator