How to calculate your RMR accurately?

For a couple of months I'm trying to get leaner, therefore I'm logging my overall food intake in order to keep a constant amount of calories deficit.

I'm a male, 22 y/o, 186 cm/6'1", 82 kg/181 lbs. Using 6 different RMR calculators, I've gotten the following results: 1875, 1878, 1968, 2167, 2253, 2254. The major disparity between the results got me wondering how do these calculators work, since they are not aware of my fat percentage and of how "fast" my metabolism is. Is there any way to estimate my RMR more precisely? In addition, your I entirely count on RMR when deciding how much calories to consume every day?

Thanks.

There is absolutely no calculator or formula that can give you a 100% accurate figure of your actual RMR. It depends on way too many factors and some of these factors aren't even understood. People have varying metabolisms, muscle mass, BMI, activity levels, environmental stress factors, external stress factors, recovery rates, genetic conditions...hence why you get different numbers from different calculators...it's almost like an insurance premium. That being said, as you can clearly see, the numbers you listed are relatively close to each other and really...that's all you need. A deficit/surplus of 12.86 calories isn't going to do much of anything, specially because this stuff matters more in the long run.

If you're trying to get leaner, I would say the absolute best RMR estimation is the one I've seen from Tnation and Layne Norton, it's worked for them and it works for me. You weight 181lbs => 181x14 = 2534 cals roughly. Now, if you wanna lose half a lbs of fat a week, then you would do (-500/600) and get around 1900-2050 ish calories. So eat anywhere between 1900-2100 calories a day in order to lose weight at a good rate.

I would always suggest starting at the highest range possible since drastically reducing calories is a sure way to slow down your metabolism and is unrealistic in the first place.

So to sum up, the calculators are all just estimations to narrow down your approximate rate. Noone except yourself can know your true metabolic rate and you actually won't until you start experimenting a bit. Which is realistically the whole goal of fitness...to learn more about your body and improve it. Start at about 2100-2200 calories a day, do this for a week or two and see if you're losing any weight, if not then reduce by another 100. When you do lose the weight, you know that the previous caloric intake goal was your maintenance rate.