I'm assuming you're asking how to do this in advance, rather than how to make each hiring decision. A few ideas:
- Hiring is only part of your wider planning process. Do you know what you need to do in the future? If so, use that as a guide.
- Hiring is only part of your wider budgeting process. You will want to create a financial plan for your business, in order to force yourself to be explicit about your assumptions, and to work out whether there is a viable business there.
- Other similar companies may provide some indication of what you need, e.g. if you're a SaaS business then you could look at other SaaS business with similar customers and deal sizes, to figure out how many sales people you need for a given volume of sales. But you should probably do your own thinking bottom up first, rather than just triangulating from external data.
