You should plan to spend 4–6 hours per day at the Singapore F1 Grand Prix to fully enjoy the experience.
Arrive by late afternoon to explore fan zones, grab food, and catch support races before the main F1 sessions begin in the evening. If you're attending concerts, expect to stay until around 10:30–11pm.
For the full experience—practice, qualifying, race day drama, and entertainment—a 3-day pass (Friday to Sunday) is highly recommended.