# Is there some formula to calculate body fat % from BMR value? [closed]

I have a Fat Scale which measures my weight, body fat %, muscle mass, bone mass, BMR, AMR etc. Its beurer BF-750. The problem with this machine is if I set my activity level different it shows my body fat % totally different. Only thing which is almost always same on all activity level is BMR. Is there any formula to calculate body fat % using BMR on my own?

## 2 Answers

There are dozens of regression equations around, that have been created over the years from studies of various different demographics, simply have a play / choose one that seems suitable e.g.    The Katch-McArdle Formula (Resting Daily Energy Expenditure):

``````P = 370 + (21.6 * LBM)
``````

Where LBM is your lean body mass, and

``````LBM = BM * (1-BF)
``````

where BF is your bodyfat ratio.

Although both the BMR and the BF values you get from your scale are very imprecise. BMR is probably calculated using something like harris and benedict formula.

• What's that P variable? – Tyler Mar 9 '15 at 20:56
• And I think OP wants to go the other way. They want BF as a function of BMR. But you could use these formulas to get such a function. – Tyler Mar 9 '15 at 21:04
• P is Resting Daily Energy Expenditure. Yes you could, but it would be at least as bad as the P approximation, which is probably very bad. – Mårten Mar 10 '15 at 7:22