Body fat percentage: how to measure it and what figure is healthy for your age
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BMI misses more than half of people with excess fat. What body fat percentage is healthy for men and women by age, and how to measure it at home with a tape measure.
Two people can be the same height, weigh the same and have the same body mass index, yet be physically very different: one with lots of muscle and little fat, the other the other way round. The scale and BMI cannot tell them apart. Body fat percentage can, and that is why it is the figure that best sums up your body composition.
In this guide you will see why BMI falls short, what body fat percentage is considered healthy for men and women by age, the methods for measuring it with their real accuracy, how to calculate it at home with a tape measure, and what to do with the number once you have it.
Why BMI is not enough
Body mass index divides weight by height squared. It is quick and useful for studying populations, but it does not know what that weight is made of. Romero-Corral and colleagues (2008) tested it on 13,601 adults from the US national health survey, comparing BMI with body fat percentage measured by bioimpedance. Using WHO obesity thresholds based on body fat, over 25% in men and over 35% in women:
- According to BMI, 19.1% of men and 24.7% of women had obesity.
- According to body fat percentage, it was 43.9% of men and 52.3% of women.
A BMI of 30 or more was almost never wrong when it flagged someone with excess fat, but it missed more than half of the people who had it. And it failed above all in the middle range, with a BMI of 25 to 29.9, in men and in older people. The reverse also happens: a very muscular person can have an "overweight" BMI with little fat.
In short: BMI works as a first approximation, but if you do strength training or want to know how you really stand, body fat percentage and waist circumference tell you much more.
What body fat percentage is healthy
There is no single universal official figure, but the most widely used reference is the work by Gallagher and colleagues (2000), published in the American Journal of Clinical Nutrition. They measured the body fat of 1,626 adults with reference methods, including dual-energy X-ray absorptiometry (DEXA), and linked it to the healthy BMI ranges of the WHO and the US National Institutes of Health. That gave them body fat ranges by sex and age. These are the ranges for the study's white population:
| Sex and age | Low | Healthy | Overweight | Obesity |
|---|---|---|---|---|
| Women 20-39 years | Under 21% | 21-33% | 33-39% | Over 39% |
| Women 40-59 years | Under 23% | 23-34% | 34-40% | Over 40% |
| Women 60-79 years | Under 24% | 24-36% | 36-42% | Over 42% |
| Men 20-39 years | Under 8% | 8-20% | 20-25% | Over 25% |
| Men 40-59 years | Under 11% | 11-22% | 22-28% | Over 28% |
| Men 60-79 years | Under 13% | 13-25% | 25-30% | Over 30% |
Three important points. First: women naturally carry more fat than men, for hormonal and reproductive reasons, so 25% does not mean the same thing for both. Second: the ranges go up with age. Third: the study itself found differences between ethnic groups, with the Asian population showing more fat for the same BMI, so these are a guide, not a verdict.
Body fat that is too low is also a problem
Dropping below the healthy ranges has costs. In women, very low body fat is associated with menstrual cycle disturbances, and in both sexes with poorer recovery, less energy and hormonal problems. The percentages seen in competitive bodybuilding are held for only a few days and are not a health goal.
How to measure your body fat: the methods and their accuracy
No method is perfect. What matters is choosing a reasonable one and always using the same one, under the same conditions, to see the trend.
| Method | Where | Cost | Accuracy | What skews it |
|---|---|---|---|---|
| DEXA | Clinic or specialist centre | High | High; it is a reference | Hydration and recent meals, to a lesser extent |
| Skinfolds | With a professional or at home with calipers | Low | Good if done by someone experienced | The measurer's technique |
| Tape measure (Navy method) | At home | Very low | Acceptable for tracking progress | Where and how the tape is placed |
| Bioimpedance scales | At home or at the gym | Low-medium | Varies between models | Strongly affected by hydration, food and recent exercise |
| BMI | Anywhere | None | Does not measure fat | Muscle mass |
Skinfolds
A caliper measures the thickness of the skin and fat pinched at several points on the body, and an equation converts the total into body fat percentage. The most widely used equations are those of Jackson and Pollock. In men, their 1978 equations correlated above 0.90 with body density measured in the lab. In women, the 1980 equations, validated against hydrostatic weighing, had a typical error of 3.6 to 4 percentage points of body fat, and the authors warned that more care was needed after the age of 40. Done well, they are a good tool; done badly, a random number.
Bioimpedance scales
They pass a weak current through the body and estimate fat from the resistance. They are convenient but very sensitive to body water: on the same day they can give different figures before and after drinking or training. If you use one, always measure fasted, first thing in the morning and after going to the toilet, and look at the trend over several weeks, not at a single reading.
How to calculate your body fat at home with a tape measure
The US Navy method was developed by Hodgdon and Beckett in 1984 at the Naval Health Research Center, validated against hydrostatic weighing. You only need a tape measure and your height, all in centimetres:
- Neck: just below the Adam's apple, with the tape angled slightly forward.
- Waist: for men, at navel height; for women, at the narrowest point.
- Hips (women only): at the widest part of the glutes.
The formulas in centimetres are:
- Men: % fat = 495 ÷ (1.0324 − 0.19077 × log(waist − neck) + 0.15456 × log(height)) − 450
- Women: % fat = 495 ÷ (1.29579 − 0.35004 × log(waist + hips − neck) + 0.22100 × log(height)) − 450
"Log" is the base-10 logarithm, the one on any calculator. Two examples:
| Person | Measurements | Result | Interpretation (Gallagher) |
|---|---|---|---|
| 30-year-old man | Height 178 cm, neck 38 cm, waist 86 cm | Around 17% | Healthy (8-20%) |
| 35-year-old woman | Height 165 cm, neck 32 cm, waist 72 cm, hips 98 cm | Around 27% | Healthy (21-33%) |
It is an estimate, not an exact measurement: in very muscular people or those with unusual fat distribution it can be off. Its great value is that it is cheap, repeatable and shows whether you are heading in the right direction.
Waist circumference: the other number that matters
Not all fat is the same. Fat stored in the abdomen, around the organs, is more closely linked to cardiometabolic risk than fat on the legs or glutes. That is why the waist is such a useful indicator. Ashwell, Gunn and Gibson (2012) analysed 31 studies with more than 300,000 adults and found that the waist-to-height ratio, meaning waist circumference divided by height, detected the risk of hypertension, type 2 diabetes and cardiovascular disease better than BMI and better than waist alone, in both men and women.
As a practical reference, 0.5 is commonly used: keep your waist to less than half your height. At 170 cm tall, that means a waist under 85 cm. If you want to reduce it, you will find the keys in how to lose belly fat.
What to do with your number
If you are above the healthy range
The goal is to lose fat while keeping muscle: a moderate calorie deficit, enough protein and strength training. That way the scale goes down for the right reasons. The full plan is in how to lose fat without losing muscle.
If you are within the healthy range
You can choose based on your goal: build muscle with a small surplus or fine-tune your definition. If you are unsure, the guide to bulking or cutting helps you decide where to start. And if your goal is visible abs, read how to get visible abs: what decides it is precisely your body fat percentage.
How to track your progress
- Measure every 2-4 weeks, always with the same method, at the same time and under the same conditions.
- Combine data: weight, waist, estimated percentage and photos. If your weight does not drop but your waist does, you are losing fat and gaining muscle.
- Watch the trend, not the day: a single reading can vary with water or food.
Conclusion
Body fat percentage says much more than weight or BMI, which misses more than half of people with excess fat. As a reference, Gallagher's healthy ranges go from 8 to 20% in young men and from 21 to 33% in young women, and they rise with age. You can estimate it at home with a tape measure and the Navy method, complement it with the waist-to-height ratio and, above all, track the trend with the same method. And if you want training that helps you move that number, Progrevia's routine generator adapts it to your goal.
- Romero-Corral A, Somers VK, Sierra-Johnson J, et al. Accuracy of body mass index in diagnosing obesity in the adult general population. International Journal of Obesity. 2008;32(6):959-966.
- Gallagher D, Heymsfield SB, Heo M, et al. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. The American Journal of Clinical Nutrition. 2000;72(3):694-701.
- Jackson AS, Pollock ML. Generalized equations for predicting body density of men. British Journal of Nutrition. 1978;40(3):497-504.
- Jackson AS, Pollock ML, Ward A. Generalized equations for predicting body density of women. Medicine & Science in Sports & Exercise. 1980;12(3):175-181.
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Report No. 84-11. San Diego: Naval Health Research Center; 1984.
- Ashwell M, Gunn P, Gibson S. Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis. Obesity Reviews. 2012;13(3):275-286.
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Frequently asked questions
What body fat percentage is healthy?
According to Gallagher's ranges (2000), between 8 and 20% for men aged 20 to 39, and between 21 and 33% for women of the same age. The ranges rise with age: for men aged 60 to 79 they reach 13-25% and for women 24-36%.
How do I calculate my body fat at home?
With the US Navy method: measure your neck, waist (and hips, for women) with a tape measure and apply its formula together with your height. It is an estimate, but repeatable and useful for tracking progress.
Why is BMI not enough to know if I have excess fat?
Because it does not distinguish fat from muscle. In Romero-Corral's study (2008) of 13,601 adults, a BMI of 30 or more missed more than half of people with excess fat, especially in the middle BMI range, men and older people.
Are body fat scales reliable?
They vary a lot between models and depend on hydration: the same person can get different figures on the same day. If you use one, always measure fasted, first thing in the morning, and look at the trend over several weeks.
What is the waist-to-height ratio?
It is your waist circumference divided by your height. According to Ashwell's meta-analysis (2012) of more than 300,000 adults, it detects cardiometabolic risk better than BMI. A common reference is keeping your waist to less than half your height.
Informational content based on the available scientific evidence: it does not replace advice from a healthcare professional. If you have an injury or a medical condition, or are pregnant, check with one before changing your training or diet.
