Is BMR seriously accurate?

Your heart is beating 24 hours a day, pumping blood around your body. Your lungs are breathing 24 hours a day, taking in the oxygen you need to breath. Those things take energy, which is what calories measure.

You use energy no matter what you're doing, even when sleeping. The BMR Calculator will calculate your Basal Metabolic Rate (BMR); the number of calories you'd burn if you stayed in bed all day.
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BMR is 1665.5.

Seriously, I don't think is right. There's no way I'd burn over a thousand calories doing NOTHING. Seriously. That can't be accurate.
I'm about 5'6", 25, obviously female, and hanging around the 184-188 mark. I eat low cal (definitely not intentional!! I try to eat before 7PM and my work doesn't always let me go grab a quick bite before I leave for my lunch break run. I mainly do cardio but I am trying to get into lifting) I'm burning about 800-1000 calories a day in exercise between 30 Day Shred and c25k and general walking, not to mention my FitBit.

yes you do. how do you think your body maintains a constant body temperature? or digests your food? or fuels the muscles that you need to use to move your arms and legs? and a 101 other things in your body... all day, every day.

now, i'm going to blow your mind even more... that BMR number above is ONLY the calorie burn if you slept all day in bed and never woke or got up. if you get up, brush your teeth, fix yourself coffee, walk to the mailbox to check the mail, and 101 other common little things you do all day, you have to multiply that by a number to account for those extra calories. if you're sedentary (work a desk job), then that multiplier is 1.2x. this means your true calorie burn for the day is right around 2000 calories.

...and this does not include specific cardio you do to lose weight, such as jogging or zumba or the elliptical.

once you understand all of this and are comfortable determining your daily calorie needs, then all you need to do is log what you eat and make sure you maintain a deficit between "calories in" and "calories out" and you'll start losing weight.

also, don't worry about when you eat. eat early, eat late... it doesn't matter. all that matters is how much.

It probably is for a person with an average metabolism. But it is still only an estimate, since the calculator doesn't take into acct lean muscle vs. fat. To get anything more than an estimate you need to get it tested. A person's BMR is 5%-15% lower than their RMR. For me it was pretty far off. My BF is 32.9%, I'm 5'1 & 144.4 lbs. 51 yrs old. The tool here says my BMR is 1217, but my tested RMR is 1066, making my BMR somewhere between 906 & 1012.

I have a BMF armband, and while I'm sleeping it says I burn about 1.1 calories a min.

So if I slept all day and did nothing else, Imy body would use 1584 calories......or 1440 of you took off 10% for error in readings.

Seems totally reasonable to me.