What you probably need
Fractional CTO
$3,500/mo
You are making decisions you will live inside for years without someone whose job is to have made them before.
Tools
Fractional CTO Cost Calculator
Four questions about your situation. Get the engagement that actually fits, what it costs, and the honest case for hiring instead.
How much does a fractional CTO cost?
A fractional CTO retainer runs $3,500 per month for four to eight hours — architecture and build-vs-buy decisions, the AI stack, and the board conversations where the technical story has to hold up. Project work is scoped separately: an AI implementation runs four to twelve weeks, a technical assessment one to two.
The honest case against hiring one
The cost argument here is weaker than the one for fractional security leadership, and pretending otherwise would be dishonest. Startup CTO base salaries average $118,708, in a $46K–$255K range, which is nothing like the $325–480K a first-year full-time CISO costs. A full-time CTO is not priced out of reach for a funded startup.
So the reason to go fractional is not that it is ten times cheaper. It is that most pre-Series-A companies do not have forty hours a week of CTO-grade decisions to make. They have four to eight, concentrated in bursts, and the rest of the role is delivery work a staff engineer does better. Hiring for the burst gets you someone underemployed and expensive, and it is the hardest hire on the org chart to reverse. Rent the judgment until the decisions are continuous, then hire.
When they are continuous, hire. Past roughly twenty engineers, a few hours a month stops covering it, and a retainer is a bridge while you recruit rather than a substitute for recruiting. The calculator will tell you that.
What "AI implementation" means here
Not a chatbot on the marketing site. AI inside the workload the business runs on: the review queue, the document pipeline, the thing your team repeats a thousand times a week. The work is model and architecture selection, the eval harness that tells you whether the output is right, the human-in-the-loop boundary for the cases where being wrong is expensive, and the cost model before you scale it — which is usually the part that decides whether the project survives contact with production.
If security leadership is what you are actually sizing, the vCISO cost calculator is the tool for that, and the math is different.