The answer all depends on your reason for working out. Are you trying to lose weight, build muscle, train for an endurance race or something else?
In general if you’re looking to maintain a healthy and fit lifestyle you should aim for 3-5 days max. If you opt for 5 days you should try to split it into three days of lifting and two days of cardio and your two non-gym days should be active rest (think walking/yoga, stretching).
A typical schedule, and one that Rachcael often uses with her clients, looks something like this:
D1 – Strength Training
D2 – Cardio
D3 – Active Rest
D4 – Strength Training
D5 – Cardio
D6 – Strength Training
D7 – Active Rest
Strength Training:
Three days per week. You should aim for no more than 45 minutes of strength training NOT including a brief warm-up and cool-down. Always make sure to stretch and/or foam roll at the end of your session. You can choose to either do full-body programs on these three days or you can break it up into specific muscle groups (chest/triceps/shoulders; back/biceps; legs/abs). The latter decision will depend on your training goals.
Cardio Training:
Two days per week. There are so many options when it comes to cardio – from running to spinning, swimming and boxing. The length of these sessions will again, depend on your training goals. But I usually recommend to my clients that at least one of these days is a shorter HIIT session. Your second session should be between 45-60 minutes and be something you enjoy doing for a longer period of time.
Active Rest:
Two days per week. These are things like yoga or walking. Aim to keep your heart rate low (as close to your resting rate as possible). You want to make sure you are using these days effectively and appropriately. You should give your body 24-48 hours(ish) between strength training sessions so scheduling your rest days in between will give your muscles the proper time to heal and recover from your workout.

So tell us, how often do you work out?