How do I calculate BMR? Really.It seems I'm either overestimating or underestimating my BMR. According to fitday, living a SEDENTARY lifestyle, I should be eating 3000+ calories to STAY at my current weight. I've been skeptical of that, so I've been limiting my calories to 1800 a day, also working out daily. In one month I've lost about 2.5 lbs. I can't even tell if that's fat or daily fluctuation in weight from shitting and pissing.I'm 310 lbs and 5'10".How many calories should I be eating? Picture randomly chosen.