How Long Should a HIIT Workout Be? The Research-Backed AnswerIs 20 minutes enough for HIIT? What about 30 or 45 minutes? Research shows the sweet spot — and why more time isn't always better for interval training.Frequently asked questionsIs TimerRush free?Completely free — no account required.Where can I try the timers mentioned in this guide?All timers are at timerrush.com. Bookmark /t/25m or /t/5m for quick one-click access.