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A Quick Guide To Estimating Body-fat Percentage

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, however it seems like I’ve found a fix for that – a quick calculation to help you to get a good estimation of your body-fat percentage that can be used to help you set up your diet more precisely.

Estimating Body-fat Percentage

It doesn’t really matter what your body-fat percentage is, you just need to get an estimation of it for your calorie intake calculations and setting your fat and protein intake targets. We don’t need to be exact, we just need to not be too far off.

Here’s a rundown of the methods we typically have available to us for measuring body fat, from most to least accurate. I’m basing this on their standard error of estimate (SEE) – which basically means how accurate they are for most people:

  1. Die in a non-too-messy way that requires an autopsy.
  2. DEXA scan~1-2% (Expensive, inconvenient, up to 5% errors on an individual basis.)
  3. The US Navy Equation based on body measurements below. ~3% (Convenient, free.)
  4. BodPod / Underwater weighing, ~3% (Expensive, inconvenient.)
  5. Body-fat caliper measurements. Skilled practitioner, ~3%. Non-skilled practitioner ~5%.
  6. BIA machines (Omron, Tanita), usually found in commercial gyms, 5-8% (Best avoided.)

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

(For Men)

Measurement Guidelines

  • 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.

Recommendations

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:

  1. 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.
  2. It will give those with particularly thick (well developed) abs, or a bloated abdomen higher readings than reality.

Now, let’s put vanity concerns aside for a moment and focus on practical concerns of getting body-fat percentage incorrect. What does that mean for your calculations?

Well, let’s say that you are a 80 kg (176 lb) male, at 15% body fat, but you calculated it to be 20%. You’ll underestimate your calorie needs by ~115 kcal. You’ll eat ~10g less protein than may be ideal, and your fat intake may be 5-8g lower than it should.

Is this a big deal? No. So I really wouldn’t worry about it too much.


Anticipated Questions

Do you have the calculation for women?

Sure thing. I didn’t include it because the majority of the site’s readers are men. Here are the full, imperial calculations for both men and women:

  • Men: Body-fat % = 86.010 x log10(abdomen – neck) – 70.041 x log10(height) + 36.76
  • Women: 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. It’ll work well for the majority of people, but you could be the exception to the rule. If this can be used to get close to what is correct, then that will do, because it’s as good as or better than whatever else most people have available.

If you believe that you have a better measurement from elsewhere then by all means, please use that. Remember, this is not being suggested a means of tracking your progress but just a start point from which to base calculations, which will need to be adjusted based on real-world progress anyway.

Now, the comment section is going to develop a natural selection bias towards people complaining about this calculation being wrong because people rarely write to say that something worked out right, and no-one ever complains if they are told they are leaner than they thought. So, before writing to tell me that, here are some reasons for inaccuracies that may be worth considering:

  1. Measurement error,
  2. Comparison with some other measurement device that was also inaccurate.
  3. You are the relatively rare exception to the people that it will work well for.

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?

I just do it by eye, looking at photos, but I’m an experienced coach so I know what to look for and ask for when I get people to take those photos. Most people reading this don’t have that available as an option, hence this guide.

If I post a photo link in the comments can you tell me what you think my body-fat percentage is?

Sorry, but no. I’ll just be flooded with requests if I do and that’s not how I want to spend my time. Besides, I think talking about specific numbers puts the focus on the wrong thing – what matters is how the body measurements combined with scale weight, strength and appearance are changing over time. Make sure you don’t screw up your chances of being successful, check out my detailed progress tracking guide here.

******

Hope this was helpful. Questions welcomed in the comments. – Andy

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Maya
Maya

i used a website that had both the navy calculator and the bmi calculator and i’m just wondering which one is more accurate? The navy calculator said i have 21.6% body fat, but the bmi calculator said i have 28% body fat, which one do i go with?

Row
Row

I used a BIA and my body fat is at 30.6%.
I added light weight training about 2-3 weeks ago and it seems like I am losing muscle mass.
The results also showed that my trunk fat percentage is the highest even though it has slimmed down.
Do the exercises for the beginner 3 help in reducing fat percentage at the trunk?
And am I eating too little?
My BKR is roughly 1162 cal. I exercise an hour 5 times a week and consume about 1400-1500 cal a day.

Thank you!

Row
Row

Based on the us navy calc, i am 23% BF (female) which i believe most of it is at my belly because i can pinch a huge amount of skin/fat from my belly.
I’ve been doing several abs exercises and have seen improvements over the month. Cardio 4 times a week. The line is more define.
Unfortunately i have not been able to stick to my daily protein intake. (I will be cooking soon so i hope I can make my meals meet the requirements daily). Added some resistance training the past 3 weeks. Going to do more resistance and heavier training from now on.
Do i need to be in a cal deficit to put on muscle but lose body fat?

Thank you so much!

Row
Row

Thanks for your help!
Yes I read it but was kind of confused if I should have a cal deficit or maintain the same.
But you just answered it. Thank you so much for your advice! I’m excited and hope to see results in a few months’ time 😀

Chris S
Chris S

Andy, just used the body fat chart and came up with 19% (not good) but weighing only 155# at 5’10” tall I feel underweight any suggestions ?

manuel
manuel

Hi Andy

Is there a Source for the SEE values you listed for the different methods? And im Not sure if i misunderstand what you Are saying But if the BIA from a commercial gym has a 8% error i Would expect the 20% to be off By up to 2% Not 8. (20×0,92=18,4 or 21,6)

thanks in advance

Adam
Adam

Hi Andy,

Came across your site a few days ago. Its excellent!

I have a question: I have been cutting since May and have lost 5kg. My daily calories are 2020. When I used your metric calculator it said I should be consuming 2629 calories. What should I do? Switch and maybe put the weight back on I have already lost or wait until I go back into my bulk phase in September before switching?

Thanks!

Devan
Devan

THANK YOU! Your writing and level of expertise is exactly what I have been looking for, for basically my whole life. Thank you for being so generous with your knowledge, tools, and experience.

Dylan Chapman
Dylan Chapman

Do you measure above the belly button or below

Sarah Uytterlinde
Sarah Uytterlinde

Hi,

For the calculation for women: are the measurements of neck, waist etc to be entered in the metrical or imperical system?
So inches or centimeters :)! Thanks!

Bill
Bill

Andy,
I have been dieting and lifting for over ten years, but this was the first time I’d seen the Navy approach mentioned. (I can’t tell you how many times I’ve read words similar to “All body fat measurement approaches suck. Just use the same one so your results will suck consistently.”) The results were in the ballpark I’d expected (19%), although your explanation that measuring the neck and abdomen makes the most sense because that’s where most people store fat was a lightbulb moment. I can’t thank you enough for providing such an excellent resource.
Bill

Vincent
Vincent

Hello Andy,

I was reading through this article and saw that you mention bloating as throwing off measurements.

What would you recommend for someone who wakes up bloated most mornings and takes measurements?

Geoff
Geoff

I am 18.1% body fat without having committed to any gym program for a few years. What would be considered a healthy fat percentage without considering aesthetics of ripped lean muscle?

Linn
Linn

Hi Andy,

Do you have a reference for your BF% equations?

Thanks in advance,

Linn

A Rog
A Rog

Andy, all of your articles are extremely well written and full of great information. Definitely the most precise and enjoyable online coaching I’ve came across thus far. Thank you for your dedication!

Eric
Eric

I can vouch for this calc. I had a DEXA scan and this calc was within 0.3% !
So, if you are a man with a typical fat distribution in the torso it is as accurate as DEXA and free !

Teun
Teun

Hi Andy,

For an optimal nutrition partitioning in realizing muscle mass, what bodyfat % do you recommend? Max 15%? for men?

Is this also a issue for women? If so, whats the maximum bodyfat %?

For men 10% bodyfast is pretty ripped, what is the equivalent for women?

Thanks in advance Andy.

Seif
Seif

What does the ~ 3 % mean for the us navy method does that means add three to your bf percentage

Nick
Nick

Andy Hi,
I’m a little bit confused. Why the narrower the neck the higher the BF ? Shouldn’t be the opposite since a more narrow neck means a thinner neck and a thinner overall body ? Thanks.

Craig
Craig

Check out this method for estimating body fat: https://strongur.io/calculator.html

All it uses is height, weight, max bench & max squat. I’ve been helping beta test his new app (it’s pretty awesome), and the body fat calculator is amazing accurate. It uses your max lifts to estimate your lean mass, and then backs into your body fat the other way.

The calculations I get from it are right in the ballpark of the Navy method, only without the measuring.

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Alex Martin
Alex Martin

Put me right at 14.7% which is pretty accurate. Thanks for this article man!

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