Here is what the research says about what your company actually needs at each stage — and what it costs to get it wrong:

Under 50 employees
Most companies under 50 employees do not have a dedicated HR person. Owners or office managers handle HR basics, often with outsourced support. This works until it does not. The risk is compliance gaps, inconsistent hiring, and people decisions made without any framework. Companies that formalize HR earlier tend to have more consistent people practices, better job satisfaction, and fewer unforced errors.

50 to 150 employees
This is where most businesses hire their first HR generalist or manager. You may see a ratio of one HR professional for every 75 to 100 employees, but faster-growing companies often need more. At this stage you need someone who can own hiring, onboarding, performance, and compliance — not just answer HR questions reactively. 

150 to 500 employees
This is where HR becomes a strategic function. You need an HR director or VP of People who sits close to the leadership team and connects people decisions to business outcomes. Most organizations see value in fractional CHRO support between 75 and 500 employees, though complexity and risk matter more than headcount alone.

500 employees and above
This is when a full-time CHRO becomes justified. The question is not so much when you need a CHRO as it is how many CHRO hours you need to execute your strategic plan. Below 500 employees most companies need the thinking and systems a CHRO would build — not the full-time salary that comes with the title.