Guide // Fractional CTO
A fractional CTO, what one actually does, and what one costs.
A senior engineering leader working part time. Same judgment as a full-time CTO, without the salary, the equity or the twelve weeks of hiring. The term has been stretched to cover everything from a genuine part-time executive to somebody answering questions on Slack, so it is worth being precise about which you are buying.
What the job actually covers
The useful test is whether someone will own these, not advise on them. Advice is cheap and everywhere. Ownership is the thing that is hard to buy.
In the remit
- Architecture and system design
- Security, auth and data boundaries
- Environments, CI/CD and deploys
- Data modelling and storage choices
- Build versus buy, and vendor calls
- Code review and engineering standards
- Monitoring, alerting and incident response
- Technical due diligence readiness
Not the remit
- Sales and marketing
- Your pitch narrative and deck
- Cap table, legals and fundraising strategy
- Design and brand
What it costs
Rates vary more than in almost any other engineering role, because the same title covers four different jobs. These are the four, with what each tends to cost.
| Arrangement | Typical cost | What you get |
|---|---|---|
| Embedded, 2 to 3 days a week | £8,000 to £12,000/mo | A genuine part-time executive. Runs hiring, owns the roadmap, sits in board meetings. |
| Around one day a week | £4,000 to £8,000/mo | The common shape. Architecture, review, and being the person accountable when something breaks. |
| Advisory, a few hours a month | £1,600 to £4,800/mo | Answers questions and reviews decisions. Does not carry delivery. |
| Day rate, ad hoc | £800 to £1,500/day | Useful for a specific problem. Expensive as a standing arrangement, and nobody owns the outcome. |
Published market data for this role is reported in US dollars. These are converted to sterling to be useful to a UK reader, so treat them as indicative ranges rather than measured UK rates. What does not vary is the shape: you are paying for seniority and accountability, and the number tracks how much of both you are asking for.
When you need one, and when you don't
Worth it
- You are raising, and an investor has asked who owns the technology.
- You have engineers but nobody senior enough to tell them they are wrong.
- You are about to make a decision that is expensive to reverse: a rewrite, a platform migration, a first technical hire.
- Something broke badly and nobody could say why.
Not yet
- You have not built anything yet. Get to something real first, cheaply.
- You want someone to write the code. That is a contractor or an agency, and it costs less.
- The decision in front of you is genuinely reversible. Make it and move on.
- You are looking for reassurance rather than a decision. That is expensive reassurance.
The cheaper option, honestly
If you need somebody embedded in the company, making decisions daily and answering to your board, hire a real fractional CTO at the rates above. Nothing below replaces that, and anyone telling you otherwise is selling.
But a lot of founders asking this question do not need a person on retainer. They need senior judgment at the few moments it changes the outcome, and someone checking their work in between. That is a much smaller thing to buy.
The Founding Engineer is that smaller thing: 8 weeks, 5 founders sharing one senior engineer, £2,500. Architecture decided with you, your code reviewed weekly, and in production by week 8 or you get it all back. Roughly a tenth of what the equivalent months of a fractional CTO would cost, because you are sharing the person and doing the building yourself.
Not sure which you need? Say so on a call and I will tell you honestly. Sending someone to hire a proper fractional CTO costs me nothing and saves them a wasted eight weeks.
If judgment is what you're short of
8 weeks, 5 seats, £2,500 for the founding cohort. In production by week 8 or a full refund.