ยท 5 min read
Fractional, interim, or part-time CTO: which one do you need?
Same title on LinkedIn, three different jobs. Picking the wrong one costs a quarter, because the mismatch only shows once the work starts.
What is the difference between a fractional and an interim CTO?
A fractional CTO leads engineering for part of the week, usually 2 to 3 days, alongside the leadership that is already there, for as long as the stage needs it. An interim CTO replaces a CTO who is gone, full time, for a bounded period, usually 3 to 9 months. A part-time CTO is the same job as a fractional CTO under an older name; the market settled on "fractional" around 2020 and the two are interchangeable.
| Model | Time | Duration | The trigger |
|---|---|---|---|
| Fractional CTO | 2 to 3 days a week | Open-ended, reviewed quarterly | There is a leadership gap but no vacancy: the team outgrew its leads, delivery drifted, the platform costs too much |
| Interim CTO | 4 to 5 days a week | 3 to 9 months, ends at handover | The seat is empty: the CTO resigned, was asked to leave, or lost the board |
| Part-time CTO | Same as fractional | Same as fractional | Same job, older name |
When do you need an interim CTO?
When the seat is empty and the org cannot wait for a search. An empty CTO seat leaks senior engineers within a quarter: they read the vacancy as uncertainty and update their profiles first, resign second. Someone has to hold hiring, the architecture calls, and the exec table full time while the search runs. That is interim work, and it ends on the day the permanent hire is up to speed, not the day they sign.
When is fractional the better fit?
When the problem is real but the seat is not empty. A VP who needs a counterweight, a team that grew past its structure, a right-sizing decision nobody inside can make cleanly, a platform bill that grew past what anyone can explain. Two focused days a week move all of those, and a full-time presence would mostly add meetings. It is also the honest fit for most SMEs: below roughly 40 people in and around software, there is rarely 5 days of CTO work in a week.
Which one costs what?
Fractional runs EUR 9 000 to EUR 20 000 a month at 2 to 3 days a week; interim runs EUR 20 000 to EUR 35 000 a month full time. The full bands and the math against a permanent hire are in what a fractional CTO costs in Europe.
The label matters less than the exit
I do both, and the question I ask before either is the same: what does the end state look like, and who holds the org after me? An engagement without a named end state does not end, it fades, and fading is expensive. The deliverable of interim work is a permanent leader in the seat. The deliverable of fractional work is an org that no longer needs the extra days. If the person you are talking to resists defining either, keep looking.
Definitions reflect how the market uses the words in 2026. You will find people who use them differently; ask about days and duration, not titles.