Is a fractional CTO cheaper than a full-time CTO?

For the first year, substantially. A median UK CTO on GBP 100,000 costs GBP 137,000 to GBP 144,000 in first-year cash once employer National Insurance, pension and recruitment are included. Two days a week of a fractional CTO is about GBP 65,000. The gap narrows in year two, when the recruitment fee falls away.

When should you hire a full-time CTO instead?

When the work genuinely fills a week and keeps filling it. In practice that means an engineering team of roughly eight or more, or a product whose technical direction changes faster than a part-time week can track. Fundraising is often cited as a trigger but rarely is one on its own.

What does a full-time CTO cost in the UK?

The median advertised UK CTO salary was GBP 100,000 in the six months to 29 September 2026 (ITJobsWatch, 59 salaries). Employer National Insurance at 15% above GBP 5,000 adds GBP 14,250, pension adds GBP 3,000 to 5,000, and a search fee typically adds 20 to 25% of salary in year one.

Fractional CTO

Fractional CTO vs a full-time hire, with the actual numbers

There is no shortage of pages comparing these two. What there is a shortage of is one that puts a number on either. I read six while writing this; not one of them priced the comparison it was making.

The full-time side

Median advertised UK CTO salary, six months to 29 September 2026: £100,000 (ITJobsWatch, 59 salaries from 73 adverts). What that actually costs to employ:

	Year one	Year two
Salary	£100,000	£100,000
Employer NI, 15% above £5,000	£14,250	£14,250
Pension, 3–5%	£3,000–5,000	£3,000–5,000
Recruitment, 20–25%	£20,000–25,000	—
Cash out	£137,000–144,000	£117,000–119,000

Equity is not in that table because it varies too much to average honestly. At seed and Series A a CTO hire commonly costs something in the low single-digit percentages, which on most cap tables is worth more than the salary.

The fractional side

UK contract CTO day rates had a £625 median over the same window, though from only 17 quoted rates. Two days a week works out at roughly £5,400 a month, or £65,000 a year. One day a week is about £32,000. Real retainers tend to sit slightly under those, starting around £2,500 a month for advisory work. The cost page has the breakdown and the sources.

Year one, two days a week vs a full-time hire

£65,000 vs £137,000–144,000

Year two: about £65,000 against £117,000–119,000. The gap narrows once the search fee falls away, but it does not close.

The number the comparison usually leaves out

Cost of a wrong hire. A CTO search takes two to four months. You find out it was the wrong person somewhere around month four or five, because that is when the first genuinely hard call gets made. Unwinding takes a notice period and another search.

Call it the recruitment fee again, a quarter of salary in wages for someone who is on their way out, and a lost quarter of roadmap. Comfortably £60,000 and two quarters, and that assumes you act quickly, which founders mostly do not. A retainer ends with a month's notice. That asymmetry is most of the actual argument, and it never appears in the comparison tables.

When full-time is the right answer

It genuinely often is, and any fractional CTO telling you otherwise is selling. Hire:

When the engineering team is around eight or more. Below that a good lead developer plus part-time direction covers it. Above it, management becomes the job, and management does not compress into two days.
When the technical direction changes faster than a part-time week can track — a platform pivot, a regulated launch, a migration with a date on it.
When the role is as much external as internal. Enterprise buyers, regulators and some investors want a named person who is unambiguously yours.
When you have tried fractional and keep running out of week. That is the clearest signal there is, and it costs one quarter to discover rather than four.

When fractional is the right answer

Fewer than about eight engineers, and the problem is direction rather than capacity.
You cannot yet describe the role well enough to hire for it. Two days a week for a quarter will write that job description far better than you can from the outside.
The decisions are sparse but expensive — a stack choice, a build-versus-buy call, whether the thing you have can carry another year.
You need someone now. A search is months; a retainer starts next week.

One honest caveat about my own position here: I sell the fractional side. Weigh the argument, not the source. The numbers above are all sourced and dated so you can check them without taking my word for anything.

Sources. ITJobsWatch permanent CTO and contract CTO, six months to 29 September 2026. GOV.UK employer rates and thresholds, 2026 to 2027. Pension and recruitment percentages are typical practice, not measured averages. The cost-of-a-wrong-hire figure is an estimate built from those inputs and labelled as one.

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