Fractional CTO vs Interim CTO vs Full-Time CTO: A Decision Framework

You need senior technology leadership. You're not sure which kind.

The market now offers three distinct models—fractional, interim, and full-time CTOs—each with different economics, time commitments, and ideal use cases. Choosing wrong costs money and time. Choosing right accelerates everything.

This guide provides a clear decision framework for UK and European founders evaluating their CTO options.

Quick Comparison: Three Types of CTO Engagement

Before diving deep, here's the essential difference:

Model	Time	Duration	Monthly Cost*	Best For
Fractional CTO	1-4 days/week	Ongoing (months to years)	£2,500-£12,000	Companies needing strategic leadership without full-time overhead
Interim CTO	5 days/week	Temporary (3-12 months)	£15,000-£30,000	Emergency cover or transition management
Full-Time CTO	5 days/week	Permanent	£12,500-£25,000 + equity	Companies ready for dedicated executive leadership

*UK/Europe market rates for experienced professionals, 2025

The fundamental question: How much CTO attention does your company actually need, and for how long?

Fractional CTO: The Part-Time Strategic Partner

A fractional CTO provides ongoing part-time technology leadership. They work with multiple companies simultaneously, typically dedicating 1-4 days per week to each client.

What a Fractional CTO Does

• Strategic planning — Technology roadmaps, architecture decisions, build-vs-buy
• Team building — Hiring strategy, interview participation, structure design
• Investor communication — Board presentations, due diligence preparation
• Crisis response — Production issues, security incidents, team conflicts
• Mentoring — Developing internal engineering leadership

What they typically don't do: day-to-day coding, daily standups, full-time people management.

When to Choose Fractional

Fractional is right when:

• You need executive-level thinking but not daily presence
• Your engineering team can operate semi-autonomously but lacks strategic direction
• You're preparing for fundraising and need to professionalise technical operations
• Budget constraints prevent a competitive full-time CTO salary
• You're between stages—past needing just developers, not yet ready for a full executive

Fractional is wrong when:

• You have zero engineering capacity and need someone to build from scratch
• Daily technical decision-making is required (fast-moving product, constant pivots)
• Your team is so large (25+) that even part-time leadership creates bottlenecks
• You're in crisis mode requiring full-time attention

Typical Costs (UK/Europe)

Engagement	Days/Month	Monthly Cost
Advisory	2 days	£2,000-£3,500
Standard	4-6 days	£4,000-£7,500
Heavy	8-12 days	£8,000-£12,000

Annual cost: £24,000-£144,000

Compare to full-time CTO: £150,000-£300,000+ fully loaded

Interim CTO: The Full-Time Temporary Solution

An interim CTO is a temporary full-time executive who fills a gap—usually while you search for a permanent hire, manage a crisis, or navigate a transition.

What an Interim CTO Does

• Everything a full-time CTO does—but with a defined end date
• Transition management — Stabilising after a CTO departure
• Turnaround situations — Fixing serious technical or team problems
• Acquisition integration — Managing technical merger work
• Permanent hire support — Defining the role and vetting candidates

The key difference from fractional: interim CTOs are fully embedded, 5 days a week, treating your company as their primary (only) focus during the engagement.

When to Choose Interim

Interim is right when:

• Your CTO just left (resigned, terminated, or transitioned out)
• You need full-time coverage while conducting a permanent search
• You're facing a crisis requiring undivided attention (major technical failure, security breach, team exodus)
• You're mid-acquisition and need dedicated leadership for integration
• Your existing CTO is on extended leave (medical, sabbatical)

Interim is wrong when:

• You could handle the situation with part-time senior guidance
• Your budget can't support near-contractor rates (£800-£1,500/day)
• You don't actually need full-time coverage—you need the right strategic inputs
• The "temporary" situation is actually permanent (you're avoiding the real hire)

Typical Costs (UK/Europe)

Interim CTOs typically charge day rates, often through specialist recruitment firms.

Experience Level	Daily Rate	Monthly (22 days)
Solid	£800-£1,000	£17,600-£22,000
Senior	£1,000-£1,300	£22,000-£28,600
Elite	£1,300-£1,500+	£28,600-£33,000+

Plus agency fees (15-25%) if sourced through intermediaries.

These rates reflect urgency and the expectation that interims find their next role once yours ends. You're paying for immediate availability and full commitment.

Full-Time CTO: The Permanent Executive Hire

A full-time CTO is exactly what it sounds like: a permanent member of your executive team, fully dedicated to your company.

What a Full-Time CTO Does

• Complete ownership of technology strategy and execution
• Daily leadership of engineering teams
• Executive presence — C-suite peer, board member, company spokesperson
• Long-term thinking — 2-5 year technical vision and culture building
• Full accountability — Success or failure is theirs

A full-time CTO isn't just more hours than a fractional—it's a different relationship. They build company-defining culture, make bets on technology direction, and stake their career on outcomes.

When You Need Full-Time

Full-time is right when:

• Technology is your core differentiator (not just operational infrastructure)
• You have 25+ engineers requiring hierarchical leadership
• You can afford competitive total compensation (salary + equity + benefits)
• Your pace of change requires daily executive decision-making
• You're at a stage where a strong CTO attracts other senior talent

Full-time is wrong when:

• You can't offer competitive compensation and will get B-players
• Your technical needs are periodic, not continuous
• You haven't validated product-market fit and may pivot significantly
• Budget constraints would force you to hire junior "in-title-only"

Typical Costs (UK/Europe)

Seniority	Base Salary	Equity	Total Comp
First-time CTO	£120,000-£150,000	0.5-1.5%	£140,000-£180,000
Experienced	£150,000-£200,000	0.3-1.0%	£180,000-£250,000
Elite/Scale-up	£200,000-£300,000	0.2-0.5%	£250,000-£400,000

Plus: NI contributions (15.05%), pension (5%+), benefits, equipment, training.

Fully-loaded annual cost: £170,000-£350,000+

And if it doesn't work out? Severance, recruitment fees, transition costs, team disruption. A bad CTO hire at £200k salary might cost £400k+ to correct.

The Decision Framework

Use these four factors to clarify your decision:

Factor 1: Your Current Stage

Stage	Typical Choice	Why
Pre-seed / Seed	Technical co-founder or advisor	Too early for any CTO model
Post-seed / Pre-Series A	Fractional CTO	Need credibility, not full-time overhead
Series A	Fractional → Full-time transition	Growing needs, but timing varies
Series B+	Full-time CTO	Scale requires dedicated leadership
CTO departure	Interim → Permanent search	Cover the gap, search properly

Factor 2: Your Budget Reality

If your monthly technology leadership budget is:

• Under £2,000 — Advisory relationship or mentorship only
• £2,000-£5,000 — Fractional CTO (1-2 days/week)
• £5,000-£10,000 — Heavy fractional or evaluate full-time
• £12,500+ — Full-time is financially viable
• Emergency (any budget) — Interim at day rates if needed

Factor 3: Your Immediate Needs

Choose fractional if:

• You need strategy more than daily presence
• Your team can execute without constant supervision
• Key decisions are periodic, not daily

Choose interim if:

• You're in crisis or transition
• You need full-time cover NOW
• The situation is temporary by nature

Choose full-time if:

• Daily executive involvement is required
• Long-term culture building is the priority
• Technology is competitive advantage #1

Factor 4: Your Long-Term Plans

• Planning to raise in 12 months? Fractional can prepare you
• Planning exit in 24 months? Interim or fractional for due diligence prep
• Building for 10+ years? Full-time is inevitable—question is when
• Uncertain about direction? Fractional preserves flexibility

Common Scenarios and Recommendations

Scenario 1: Non-technical founder, seed-funded, 3 developers

Fractional CTO (1-2 days/week). You need strategic oversight and a translation layer between business and engineering. Full-time is overkill; you can't afford to pay for 5 days of CTO time when 1-2 days of the right guidance is what matters.

Scenario 2: CTO just resigned, Series A company, 15 engineers

Interim CTO immediately, then conduct proper permanent search. Don't rush the full-time hire out of panic. Interims buy you 3-6 months to find the right person.

Scenario 3: Series B, 40 engineers, need someone to own AI strategy

Full-time CTO or VP Engineering + Fractional AI specialist. At this scale, you need dedicated leadership—but specialist expertise (AI, security) can still be fractional.

Scenario 4: Pre-exit preparation, 6-12 month horizon

Fractional CTO focused on due diligence readiness. Hiring full-time for a 12-month runway wastes equity and creates unnecessary complexity.

The Hybrid Approach

Many companies combine models:

• Fractional CTO + Full-time VP Engineering — Strategy from senior expert, day-to-day from internal leader
• Full-time CTO + Fractional specialists — Permanent leadership with outside expertise for AI, security, or specific domains
• Interim CTO → Fractional transition — Full-time crisis coverage that steps down to ongoing strategic support

The models aren't mutually exclusive. Think about what combination serves your needs at each phase.

Making the Right Choice

The mistake isn't choosing one model over another—it's forcing a situation into the wrong model because of assumptions about how technology leadership "should" work.

A £200k full-time CTO solving £50k worth of problems is a waste.

A £4k/month fractional CTO applied to a situation requiring daily presence is a frustration.

Match the model to reality: your stage, budget, needs, and timeline. The right structure serves the business. The wrong one creates new problems.