Two days covers the tower and one museum if you pre-book. Five days is the comfortable minimum for Versailles without treating the Métro as the holiday.
2 days: landmarks only
Day one: Eiffel Tower (dusk if you can), Champ de Mars, Seine walk. Day two: Louvre or Musée d’Orsay, then Notre-Dame and a Marais evening. Skip Versailles.
3 days: city plus neighbourhood
Keep the two-day core, then give day three to Saint-Germain or the Latin Quarter with no major ticket. This is the version that still feels like Paris rather than a queue.
5 days: Paris and Versailles
Three city days, one Versailles weekday (early RER, Hall of Mirrors, gardens), and one buffer for rain or a second museum. Stay in Saint-Germain, the Latin Quarter, or the Marais so you are not commuting into the centre each morning.
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