How do I measure bodyfat at home?
With a tape measure. The US Navy method uses your height, neck and waist, plus hips for women, and lands within a few points of a lab scan for most people. A bodyfat scale gives you a daily trend but can miss by more. For one precise number, get a DEXA scan.
How each method does
| Method | One measurement | Tracking change |
|---|---|---|
| Tape (Navy method) | In 609 Marines, about 2.5 points low for men and up to 2.3 points high for women, on average | Missed much of the change in 8 weeks of Army basic training |
| Home bodyfat scale | About 3.5 points low to 12 points high, depending on the model | Typical error of about 2 to 3 points over 3 to 4 months |
| DEXA scan | The scan the tape studies above were checked against | Repeat scans agree within about 1% of the value |
The tape is not perfect. In 2023, a study of 1,407 Army recruits found the tape put them about 6 points under a DEXA scan before training. Over 8 weeks, DEXA showed bodyfat falling 3 to 4 points while the tape showed 0 to 2.
Measuring bodyfat at home is like checking a room’s temperature with your hand. You’ll be a few degrees off, but you’ll notice when it gets warmer.
What we’d do
- Track your waist itself, in inches. Every tape formula is built on it, and the US risk lines use it directly: over 40 inches for men or 35 for women.
- Use the tape calculator once a month, same tape, same spots, same time of day, and treat the result as a range.
- Weigh every morning if you have a bodyfat scale, and watch the monthly trend.
- Get a DEXA scan once if you want a true starting point, then again months later on the same machine.
How to take the tape
Measure on bare skin, with the tape snug but not pressing in. Men: the neck just below the Adam’s apple and the waist at the belly button. Women: the neck, the waist at its narrowest and the hips at their widest. Take each twice and use the average.
5 sources
- Potter et al., Circumference-based predictions of bodyfat revisited: preliminary results from a US Marine Corps body composition survey, Frontiers in Physiology, 2022pubmed.ncbi.nlm.nih.gov
- Foulis et al., Body composition changes during 8 weeks of military training are not accurately captured by circumference-based assessments, Frontiers in Physiology, 2023pubmed.ncbi.nlm.nih.gov
- Siedler et al., Assessing the reliability and cross-sectional and longitudinal validity of fifteen bioelectrical impedance analysis devices, British Journal of Nutrition, 2023pubmed.ncbi.nlm.nih.gov
- Hind, Oldroyd and Truscott, In vivo precision of the GE Lunar iDXA densitometer for the measurement of total body composition and fat distribution in adults, European Journal of Clinical Nutrition, 2011pubmed.ncbi.nlm.nih.gov
- National Heart, Lung, and Blood Institute, Assessing your weight and health risknhlbi.nih.gov
