As said above you can not exactly say the number of bugs that an application has. Apart from that it also depends on various factors like...
complexity of the application
Skill level of the developers involved in that
Amount of rework involved in the project
level of standards in development maintained and checking done at the coding level etc.
If your company is product based then the chances are that you can predict the number of bugs to a certain extent.
If your company is project based then you will be developing it based on the client requirements. Here prediction is difficult.