I work on 2200 as being the flat amount that my body needs. That was after a lot of research, as opinions vary. This is assuming you are a man of average height height. Say 5'10-6'2
I've shed about 7 stone in a 2 year period and for me it's been a mixture of diet and exercise. There is an idea that buying some additional help in, such as a treadmill, will force the issue- it doesn't. In fact it can become a false comfort and make things worse.
Work out how many calories...