TDEE calculation with walking and going to gym

MarlaVSings

I am trying to calculate an accurate TDEE for myself but am a bit confused on level of activity and their definitions. I tried searching this topic but didn't find my answer, so hopefully someone can shed some light on this.

When calculating TDEE, I am assuming I should pick sedentary because I work a desk job. I also walk daily and have a pedometer to make sure I get 10k steps/day. Would that still put me in the category of "sedentary"?

--for the record, I also have been going to the gym 4x/week, but I think my TDEE calculation is too high. What I am trying to do is figure out how much I burn being sedentary, if that includes 10k steps per day or if I should be adding those calories separately. Then I would like to add calories burned at the gym.

Sorry if this may be confusing, but I'm wondering if sedentary assumes you are walking any amount, or if you are literally sitting on your behind for almost all of the day.