A fractional CTO and an interim CTO are both senior technology leaders hired from outside. The difference is hours and duration. The interim works full-time for a defined period, usually three to nine months. The fractional works a set number of hours or days a month for as long as the company needs.
When an interim CTO fits
Interims fit situations where an engineering team needs full-time leadership now. The CTO or VP of Engineering left and the team of ten engineers is drifting. A platform rebuild or a cloud migration is under way and needs someone to make decisions daily. A security incident needs a technical leader in the room for weeks. A carve-out from a larger company requires the systems to be separated on a deadline. In each case, the interim keeps delivery moving and hands over to a permanent hire or a fractional.
Interim CTOs are priced as full-time executives: roughly $18,000 to $35,000 a month, or $1,200 to $2,500 a day.
When a fractional CTO fits
Fractional fits when the company needs technical judgment more than technical management. A non-technical founder with an outside development shop, a company with two or three engineers, or a business preparing for due diligence rarely needs 40 hours a week of CTO time. Published fractional CTO fees run from about $3,000 a month for advice to $15,000 for an embedded role, and many work month-to-month.
Comparing cost and fit
Six months of an interim at $25,000 a month costs $150,000. Six months of a fractional at $7,000 costs $42,000. If a team of ten engineers is producing nothing without daily direction, the interim pays for itself in salary costs alone. If the team is two engineers and an agency, the interim will spend much of the week on work an engineer could do.
The private equity case
PE firms commission technical due diligence before an acquisition, and fractional CTOs often perform it. After the deal, two patterns appear. If the acquired company’s technology leader leaves or the platform needs significant work, an interim CTO may lead for the first six to nine months. For smaller portfolio companies, a fractional CTO often oversees technology across the hold period, sometimes for several companies in the same fund. Carve-outs, where a business is separated from a parent, are a classic interim case because shared systems must be split before a transition services agreement runs out.
The exit case
Technical due diligence looks for a few things: whether the company owns its code and accounts, the licenses of the open-source software it uses, security practices, the state of technical debt, whether the system can scale and whether the knowledge sits in one person’s head. A fractional CTO brought in 12 to 24 months before a sale has time to fix the findings in advance: tidy up IP assignments, document the architecture, address security gaps and reduce key-person risk. An interim during the sale can answer the questions but cannot change what the reviewer finds.
Moving between the two
Many fractional CTOs take interim assignments between retainers, and some will scale up for a quarter during a migration. If you expect a heavy period, agree the higher rate and the step back down in advance.