I had my RMR tested today - it's 1810. Can I use it to calculate TDEE in place of BMR? How interchangeable are they?

And I'd be grateful if anyone can weigh in on what my activity level might be. I wear a Fitbit and get about 6000 steps a day, but a good chunk of that is in a concentrated walk with the dogs. I also do Jillian Michaels Body Revolution, which is roughly 30 minutes of cardio and light weight training 6 days a week. Aside from these things, I end up sitting a lot.

Thank you for your help!