Short answer: 7 nights is the sweet spot for first-time visitors. Here's what fits into every length.
Stay: Istanbul only. Sultanahmet or Beyoğlu. Do the Old City day, the Beyoğlu day, and a Bosphorus ferry. Don't try to add Cappadocia.
Stay: 2 nights Istanbul + 2 nights Cappadocia + 1 flex. Internal flight both ways. This is the canonical "first Turkey trip." See our 5-day combo itinerary.
Stay: 3 Istanbul + 3 Cappadocia + 1 buffer. Or split as 2 Istanbul + 2 Cappadocia + 3 Antalya/Bodrum for a beach finish. Our favorite length.
Stay: Istanbul + Cappadocia + Ephesus/Pamukkale + Mediterranean (Antalya or Fethiye). A real Turkey overview.
Stay: Add a food-focused weekend in Gaziantep or a nature leg in Rize / Trabzon Black Sea highlands.
Stay: Work in the lesser-visited: Mersin east coast, Mardin, Van. Or settle into a digital-nomad base in Mahmutlar / Izmir.
Activate these from home — cheaper and simpler than sorting them at the airport.