Body Fat Percentage Calculator
Use a soft tape measure to estimate body fat from body circumferences. This calculator applies the classic Hodgdon-Beckett US Navy tape equations for neck, waist, height and, for women, hips. It is best for watching trends over several weeks; use DEXA or a qualified clinician when accuracy or health decisions matter.
How the tape method works
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1
Measure your neck
Place the tape just below the larynx, keep it level all the way around and hold it snug without pressing into the skin.
-
2
Measure your waist
Men measure at the navel. Women measure at the narrowest point, usually 2-5 cm or 1-2 inches above the navel.
-
3
Measure hips if needed
For women, measure around the widest part of the hips or buttocks with feet together.
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4
Review the estimate
The calculator returns body fat percentage, fat mass, lean mass and an ACE reference band. Treat it as a screening estimate, not a diagnosis.
Formula used
Men: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Women: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
Where:
waist,neck,hipandheightare measured in inches.- Metric entries are converted internally before the formula runs.
ACE reference ranges
| Category | Men | Women |
|---|---|---|
| Essential fat | 2-5% | 10-13% |
| Athletes | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| High | 25%+ | 32%+ |
Tips for accurate tape measurements
- Measure bare skin, since clothing can compress or add thickness.
- Relax your abdomen, without pulling it in or pushing it out.
- Keep the tape level and parallel to the floor at every site.
- Take three readings and use the average. A quarter inch or half centimeter can shift the result.
- Measure at the same time of day, ideally in the morning before food or training.
Method comparison
| Method | Typical role | Best use |
|---|---|---|
| DEXA scan | Imaging-based lab estimate | Baseline or clinical follow-up |
| Hydrostatic weighing | Lab test based on underwater mass | Research or sports science settings |
| Bod Pod | Air-displacement lab test | Paid facility measurement |
| Classic US Navy tape method | Circumference estimate with several points of possible error | Free trend tracking at home |
| Skinfold calipers | Technician-dependent fold measurements | Coaching when the same trained person measures |
| Bioimpedance scale | Hydration-sensitive electrical estimate | Frequent weigh-in trends, not a single truth |
Frequently Asked Questions
It is usually useful for trend tracking, but it is still a circumference equation. Expect several percentage points of possible error, especially for very lean athletes, people with high body fat, pregnancy, swelling or unusual fat distribution.
For many people, a tape measure is more repeatable than a bioimpedance scale because hydration, meals and hard workouts can move scale readings. Use one method consistently instead of mixing numbers from different devices.
Every 2-4 weeks is enough for most training or weight-loss plans. Shorter intervals often measure tape placement noise rather than real body composition change.
The women’s equation includes hips because lower-body fat distribution can change the estimate substantially. Keep the hip tape horizontal and measure the widest point each time.
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