If the number (and type) of people staffing your business drives your revenue, then your forecast should be a brutally honest estimate of the number of people you believe your team can recruit, absorb, train, and retain over the next year. Unless you plan on using radically new tactics (such as hiring a recruiter, sponsoring visas, accepting remote applicants, etc.), your percent growth of your team in the past is the best predictor for the future.
Multiply your target team size by the average revenue per team member, and you've created your forecast.
To construct a range, think through a realistic worst case scenario (like a competitor poaching your top employees) and a best case scenario (like you suddenly become the place to work after going viral on TikTok).
This approach is simple, but enough to get you started. Want to talk through a more detailed approach? Reach out to our business coaches or ask for more help!