As lots of people already said, your user growth projection is probably not going to be very exact. ARPU can be pretty close. Expenses can be really close. Dep

As lots of people already said, your user growth projection is probably not going to be very exact. ARPU can be pretty close. Expenses can be really close. Depending on your product, you might be able to set up some initial targets and just run with those. I.e. if your marketing plan is to start at colleges (or one particular college that you have strong affiliation with), you can calculate a growth for that slice of your market. Since you are pretty set on creating a model, this will probably help you get closer. I.e. your user acquisition went from a geometric curve to more lumpy. Kinks in your curve are a good indication you gave it some thought. I.e. is there a point at time where you switch to a more aggressive growth by buying users? If you have some goals in mind of when you want to hit profitability, you can backout a user growth rate. So you have ARPU and a pretty good idea of what your expenses will be, just divide expenses by ARPU and you have a user target. So if you then have a goal of hitting break even in 13 months, you know that you will need a x factor of geometric growth. You can make this more complicated by changing your ARPU (I don't know your business model but probably ARPU goes up as you hit critical mass?). Again, probably still a BS hockey stick but hope this helps!