Last Updated: April 9th, 2020
Finding your body-fat percentage is an imprecise endeavor.
The methods that we generally have available to measure it range from being ‘acceptably accurate’ to ‘very poor,’ and they are nearly all useless for tracking changes over time. They’re all marketed as being really accurate of course, but that’s just because people are after your dollars.
The lack of a guide on this site to help you find this has been something that has bugged me for some time.
On the one hand, I recommend that people do not try to track their body-fat percentage because of the errors of all the devices we have available to estimate it. On the other hand, I use body-fat percentages in my guide to helping people decide when to cut and bulk.
This guide US Navy method combined with my new visual guide to body fat percentage fills that void.
The Issues Of ESTIMATING BODY-FAT PERCENTAGE
Here’s a rundown of the methods we typically have available to us for measuring body fat, from most to least accurate. The numbers given are the individual error rates that have been observed:
- DEXA scan. ~5%
- The US Navy Equation ~3–4% (Convenient, free.)
- BodPod / Underwater weighing, Up to 5–6% (Expensive, inconvenient.)
- Body-fat caliper measurements. Skilled practitioner, ~3%. Non-skilled practitioner ~5%.
- Bioelectrical Impedance Analysis (BIA) machines. Up to 8%.
So, if you use a BIA machine and get a reading of 20%, your actual body fat could be anywhere from 12–28%. If you use the US Navy equation and get a reading of 20%, your actual body fat could be anywhere from 17-23%. This is the difference between being useless and helpful.
Here’s that US Navy formula. Take a look and then we’ll get into some practical recommendations.
US NAVY METHOD OF BODY FAT ESTIMATION
- Height – Get someone else to do it for you if possible.
- Stomach – Measure at the navel. Have a relaxed stomach, exhaled but, don’t forcefully push it out!
- Neck – Keep your head straight, look forward. Keep your shoulders down and relaxed.
- Measure three times for each and average the three.
Simple as that.
Things To Watch Out For
The US Navy equation wins out on convenience and cost, this is what I’d recommend for most people. Notice that the reading is heavily determined by the measurement at the navel. Two important things to point out in regards to this:
- Fat comes off of the stomach/torso generally from the top down. Past the point of 10% body fat, the mid-stomach measurement (that at the navel, which the equation uses) will change very little as the person gets leaner because most of the fat is coming off from the lower abs and back at this point. Therefore, if you’re already very lean, this won’t work well for you. It will be best to estimate from pictures or use calipers.
- It will give those with particularly thick (well developed) abs, or a bloated abdomen higher readings than reality.
Do you have the calculation for women?
Sure thing. I didn’t include it because 86% of the site’s readers are men. Here’s the imperial calculation:
- Body-fat % = 163.205 x log10(waist + hip – neck) – 97.684 x log10(height) – 78.387
This looks inaccurate for me…
Yes, you may be right.
If you believe that you have a better measurement from elsewhere then by all means, please use that. Remember, this is not being suggested as a method of tracking your progress, but just a way to gauge where you might currently be at.
If you’d like to read the full US MoD paper on the way the formulas were developed so you can make your own decision, you can get that here.
How do you gauge body-fat percentage when setting things up for clients?
Visually. Check out my visual guide to body-fat percentage.
Hope this was helpful.
Questions welcomed in the comments. – Andy