As a software entrepreneur it can be difficult to know when to expand staff, marketing, etc. One simple method I developed over the years is called GPA (Growth Plan Assets). The method is really simple in that you add together cash in the bank and current accounts receivable and then divide by last month’s “normal” costs. This, in a rough fashion, gives you the number of months you can operate without any new sales.
You know you’re ready to expand when your GPA is greater than a standard college GPA (scale 0 – 4). So, like a college GPA, most of the time you’re in the two or three month range. When you go above that, you have a sufficient GPA to expand. When you are below a two, you’ll have some tough decisions to make. What’s your GPA?
Note: The higher the percentage of revenue that is recurring, the lower the desired GPA.
David Cummings on Startups 