What Is My Actual Activity Level?

How can I determine my actual activity level when using calorie calculators to estimate my maintenance calories? There seems to be a big difference between the activity levels, and I don't want to overestimate my calorie needs and mislead myself.

I work out 3 times a week, following a full-body (FB) routine. After each workout, I do 20–30 minutes of treadmill cardio at a 15% incline and 3.2 km/h. Sometimes, I also go to the gym just to do treadmill cardio. My average daily step count is around 5,000 steps.

Would you consider this sedentary, lightly active, or moderately active? How can I accurately determine my activity level and maintenance calories?