Owners ask this question as though there's a number. Twelve people. Two million. Somebody on a podcast said fifteen.
There isn't a number, and using one is how you end up with an expensive person supervising a company that didn't need supervising yet.
The actual trigger
Look at last week. Sort your hours into three buckets.
Work only you can do. Selling the large ones, the relationships that exist because of you, the calls on direction and money that genuinely require the owner.
Work anyone competent could do with the right definition. Approvals, scheduling, quoting, answering the same question again.
Work that exists because nobody's coordinating. Chasing, reminding, finding out where something got stuck, re-explaining, putting out the fire that started because two people each thought the other had it.
If the third bucket is bigger than the first, you need a manager. That's the whole test, and it's independent of how many people you have.
Ten people with clear ownership need almost no management. Six people whose work overlaps constantly need it badly.
What you're actually buying
Not more output. More capacity in the coordination layer, which is the layer you're currently occupying.
This is where owners get the hire wrong. They hire a senior version of the delivery work, the best technician they can afford, and then that person keeps doing delivery, because that's what they're good at and what feels urgent. The coordination doesn't get done, so it flows back to you, and now it costs you a salary too.
A manager's job is that they own the outcome of other people's work. If that sentence doesn't describe the role you're writing, you're not hiring a manager. You're hiring a senior doer, which may be exactly what you need, but don't expect your calendar to change.
The three things you have to hand over with it
A manager without these is a coordinator with a better title, and they'll quit inside a year.
Decision rights, in writing, with a dollar figure. They can spend up to this much without asking. They can make this category of call and tell you after. Be specific, because vagueness defaults to asking you, and asking you is what you were trying to stop.
The authority to set the standard. They get to say "we don't do it that way here" and have it stick. If only you can say that, they can't manage.
Access to the numbers their job is judged on. You can't hold someone to an outcome they can't see. If the only person who knows the margin is you, every conversation about performance is you telling them what you think happened.
Handing these over feels like the risk. Not handing them over is the reason the hire fails, and then the conclusion is that good managers are hard to find. See why your managers won't decide without you.
Internal or outside
Promoting works when the person already sets the tone informally and others already go to them. You're ratifying something true. It fails when you promote your best technician as a reward, which removes your best technician from the work and puts them in a job they didn't want and can't yet do.
Hiring from outside works when you need a standard that doesn't exist in the building. It fails when the company's actual way of working is unwritten, because an outsider can't learn it by absorption fast enough, and they'll spend their first six months discovering rules nobody told them. See why nobody follows the process you wrote.
Either way, the work needs to be specified first. That's the real prerequisite, and it's the one owners skip because it's slow and nobody's asking for it.
What it costs to wait too long
The cost isn't the growth you didn't get. It's the people you lost.
Capable employees in an unmanaged company hit a ceiling quickly. Nobody owns their development, nobody sees their work closely enough to judge it fairly, and nobody can promote them. So they leave, and the reason they give is money, and it wasn't money. See why your employees keep quitting.
That's the compounding part. Every month you delay costs you a bit of your bench, and the bench is who you'd have promoted.
What the data shows about this band
Two thirds of the owner-led companies in the Platform One Index are under $1M, and that's where this question lives.
Under $250K, 56 percent name people as the constraint, and in that band the person is nearly always the owner. There's genuinely nobody to hand to yet, so the answer isn't a manager. It's writing the work down so a manager becomes hireable.
People is the most named constraint overall at 46 percent, more than marketing and finance combined, and the lowest scoring of the five areas measured at 32.9 out of 100. The pattern in owners' own words is consistent: they know they need to hand work off, and they either can't afford it or don't trust anyone with it. A first manager is the moment you find out which of those two it actually was.
Start with the measurement
Twenty questions, about ten minutes, free.
You'll get scored in five areas and see which one your answers point at. Worth doing before you write the job description, because the role you need depends entirely on which bucket your week is actually full of.