What is a fractional CTO, what do they do and when does a startup need one?

What does a fractional CTO actually do?

A fractional CTO makes the technical calls a non-technical founder should not make alone, then makes sure the people building the product follow them. The work usually falls into five areas:

• Architecture and stack: which technologies to use, where to host, what to buy and what to build.
• Scope and roadmap: turning business goals into a realistic first release and a sensible order of work.
• Vendors and hiring: writing briefs, judging quotes, reviewing code, designing and running interviews for the first engineers.
• Security, data and quality: building in data protection by design and security proportionate to risk, which the GDPR requires in Articles 25 and 32 if you serve EU users; testing, releases, backups.
• Investors: explaining the technology in the pitch and handling technical due diligence before a round.

Fractional CTO vs full-time CTO vs technical co-founder: what is the difference?

The difference comes down to time, pay and how much risk they share with you. Here are the four options non-technical founders weigh most often.

That median covers many kinds of technology managers, and startup packages mix salary with equity, but it explains the appeal of the fractional model: you buy the judgement without the full-time cost. What you do not buy is the commitment. A technical co-founder shares the risk and stays for years; a fractional CTO has other clients and a contract that ends. Many startups use the second to get to the first, or to prepare a full-time CTO hire after the round.

When does a startup need a fractional CTO?

You need one when expensive technical decisions are coming and nobody on the team can make or check them. The usual moments:

1. You are about to sign your first development contract and cannot judge quotes that are far apart.
2. You have a prototype built with no-code or AI tools and need to know whether it can take real users.
3. An investor has asked for technical due diligence, or a credible technology slide.
4. You are hiring your first engineers and do not know how to assess them.
5. Your current vendor is slowing down, releases keep breaking and you cannot tell why.

If the scope is small and already clear, a well-chosen vendor may be enough on its own. Our checklist on how to choose a software development company helps with that.

How much does a fractional CTO cost?

Cost depends on hours, duration and responsibility, not on the title. Published rate surveys are thin and mostly vendor-written, so treat any single figure with suspicion. These are the factors that actually move the price:

• Commitment: a few hours a month of reviews and advice, or fixed days every week with team meetings.
• Accountability: advice only, or ownership of decisions, vendor management and on-call duty during incidents.
• Stage: setting up a product from scratch takes more hours than overseeing one already in production.
• Length: a short engagement to get ready for a round is priced differently from an ongoing relationship.
• Form of payment: cash only, or cash plus a small equity stake, in which case vesting rules apply; see our guide to equity splits with technical people.

What should the first 90 days look like?

The first quarter is for getting things in order, making the decisions that are hard to reverse and leaving rules that work when the CTO is not in the room.

What are the risks of the fractional model?

The main risk is a conflict of interest: if your fractional CTO works for the same firm that builds your product, they are reviewing their own work. That is not automatically a problem, but it should be explicit. Ask who reviews the code, how priorities are set and what happens if you want to change vendor. The other risks are easier to handle: limited availability (put response times and on-call terms in the contract) and knowledge leaving at the end (insist on documentation and on accounts in your company's name, as covered in who owns the code in a software contract).