Proper way to determine BMR

[hookdup]

I've been on several websites that calculate your basal metabolic rate for you, but none of them ask for my body composition or bf amount.
But doesn't the amount of body fat determine your bmr? And aren't a lot of us (well, a lot of YOU, for now) under the average 19 - 24% body fat?

Does this make a substantial difference.

I'm trying to make sure I have a calorie deficit of 500 cals per day (from diet & exercise) so even a difference of 100 cals helps.

I've done a search and haven't found any info on this except how to calculate your general bmr.

Does anyone have a link to a site that takes your bf into consideration when calculating your bmr?

 

[SteelWeaver]

Don't know about sites, but over on the diet board people always say your body weight in pounds x 15, then minus 500.

Which works out to about the same as bodyweight in pounds x 12, like spatts said, which is a good starting point, then adjust down to x 11 or x10 depending on how things go.