Fractional CTO Cost UK: What You Get for £1,500 to £6,000 a Month

A fractional CTO in the UK costs £1,500 to £6,000 a month on retainer, or £800 to £1,500 a day for ad hoc work. Some take a small equity stake in exchange for a lower cash fee. That is the short answer, and if you only came for the number, you have it.

The longer answer matters more, because the range is wide and the cheapest option is not always the cheapest outcome. This article breaks down what each pricing model actually buys, what a full-time CTO really costs once you add everything the salary figure hides, and how to tell when the fractional price stops making sense for your company.

The retainer model: what each tier buys

Most UK providers, including Prodevel, price around days per month with a three-month initial commitment, then month-to-month with 30 days' notice. The tiers look similar across the market, so here is what the money buys at each level:

• **Starter, £1,500/month (2 days):** built for pre-seed and seed companies with fewer than five people. You get a monthly strategy session, architecture reviews before big decisions, async Slack access for questions that cannot wait, and a board-ready technology update. Two days sounds thin. For a three-person team it usually is not, because the hard decisions arrive monthly, not daily.
• **Growth, £3,000/month (4 days):** for post-seed and Series A companies with 5 to 20 engineers. Weekly calls replace monthly ones. Hiring support becomes real work: job specs, interview loops, final-round calls. Vendor evaluation and investor reporting join the list. This tier exists because at this stage problems compound weekly.
• **Enterprise, £5,000 to £6,000/month (6 days):** Series B and regulated sectors. The fractional CTO sits inside the leadership team, owns technical strategy end to end, and handles compliance-aware decisions in sectors like healthcare and finance where a wrong call has legal consequences.

Notice what scales between tiers: not the quality of advice, but the surface area. A Starter client gets the same person and the same judgement as an Enterprise client. They get less of their calendar.

Day rates: flexible, but you lose the thread

Day rates in the UK run £800 to £1,500 depending on seniority and sector. The model suits genuinely bounded work: an architecture review before a rebuild, a second opinion on an agency proposal, technical support during a due diligence week.

The weakness is continuity. A fractional CTO on retainer carries context between sessions. They remember why you chose Postgres, which engineer is flight-risk, and what the board worried about last quarter. A day-rate engagement starts cold every time, and you pay for the warm-up.

A reasonable rule: if you expect to need someone more than twice a quarter, the retainer is cheaper per useful hour, not just more convenient.

Equity hybrids: cheaper cash, expensive if you win

Some fractional CTOs accept 0.5 to 2% equity in exchange for a reduced cash fee. At pre-seed, when cash is short and the equity is cheap, this can work for both sides.

Three things to check before signing:

1. Vesting. Equity should vest monthly over the engagement, with a cliff. A fractional CTO who leaves after eight weeks should not keep two points of your company.
2. Whether the discount is real. Compare the reduced fee plus equity value at your current valuation against the plain cash price. Some hybrid offers are simply the full price plus free equity.
3. What happens at the end. Agree upfront whether unvested equity lapses cleanly when either side ends the engagement.

If the maths feels hard to check, that is a signal in itself. A good fractional CTO will walk you through the comparison honestly, because the alternative is a resentful cap table conversation two years later.

What a full-time CTO actually costs

The comparison everyone makes is against the full-time salary, and the salary is the smallest part of the gap. A full-time London CTO costs £120,000 to £180,000 in base pay. Then the rest arrives:

• **Employer National Insurance:** roughly 15% on top of salary, so £18,000 to £27,000 a year.
• **Pension contributions:** 3% minimum, and senior hires expect more.
• **Recruitment fees:** executive search runs 20 to 30% of first-year salary, so £24,000 to £54,000, paid once but paid upfront.
• **Equity:** 1 to 4% for a genuine CTO hire. At a £5m valuation that is £50,000 to £200,000 of your company.
• **Time:** a 3 to 6 month hire cycle, during which the problems you wanted them to solve keep compounding.

Fully loaded, year one of a full-time CTO costs a seed-stage company £170,000 to £270,000 plus equity. That is the number to compare against a retainer, not the base salary.

The monthly comparison

Put side by side, the options look like this:

Two things stand out from the table. Day rates only undercut the retainer if you use fewer days, and the moment you use the same number of days you pay more for less. And the full-time monthly figure looks closer to Enterprise tier than founders expect, until you remember it comes with equity, notice periods, and the cost of a wrong hire.

When the fractional price stops making sense

The model has a ceiling, and an honest provider will point at it before you hit it. If you consistently need more than 6 days a month of technical leadership, the economics flip. At 10 days a month you would pay £8,000 to £12,000 on fractional terms, and at that point a full-time hire, or an interim while you search, costs about the same and gives you someone in the building every day.

The usual signs you have outgrown the model: your fractional CTO is in every hiring loop and every vendor call, decisions queue up between their days, and the engineering team has grown past 20 people. None of these are failures. The point of the model is to get you to that stage without spending £200,000 a year on the way.

Judging value beyond the price

Price tells you what you spend. It does not tell you what you get, and the spread in quality between two providers at the same price is wider than the spread in price. Things that separate a £3,000/month engagement that pays for itself from one that quietly becomes an expensive call:

• **Written deliverables.** Audits, board updates, hiring scorecards, architecture decisions with reasoning. If the thinking only exists in meetings, you are renting a conversation.
• **Decisions they prevented.** One avoided rebuild or one bad senior hire caught at interview covers a year of Starter tier. Ask providers for examples of things they talked clients out of.
• **A path to not needing them.** The right fractional CTO hires their own replacement eventually. Ask how they have handed over to full-time CTOs before.
• **References at your stage.** A founder reference from a five-person seed company tells you more than an enterprise logo.

One question cuts through most sales polish: ask what they would do in their first two days with your company. A vague answer at the pitch stage does not improve after you sign.