Why 2026 Updates Matter
We've updated our tool for 2026 to include the Relative Fat Mass (RFM) formula. Research from late 2018 through 2024 suggests RFM is often superior to BMI for predicting whole-body fat percentage, providing a simpler yet highly effective alternative to the traditional Navy method.
US Navy Method vs. Relative Fat Mass (RFM)
Unlike basic BMI calculators that only look at weight and height, our dual-method calculator uses your body measurements to distinguish between fat and muscle mass.
US Navy Method
The military standard for decades.
- ✓ Accounts for neck (muscle) size
- ✓ Widely validated against hydrostatic weighing
- ⚠ Requires more complex measurements
Relative Fat Mass (RFM)
The modern, data-driven alternative.
- ✓ More accurate than BMI for obesity prediction
- ✓ Simple: Height-to-Waist ratio checks
- ✓ Validated in large population studies (NHANES)
How to Measure Correctly
Precision is key. Use a non-stretchable measuring tape and follow these guidelines:
1
Waist (Men & Women)Men: Measure at the navel (belly button).
Women: Measure at the narrowest part of the abdomen (usually just above the navel).
Women: Measure at the narrowest part of the abdomen (usually just above the navel).
2
Neck (Men & Women)Measure just below the larynx (Adam's apple). Keep the tape slightly angled down at the front.
3
Hips (Women Only)Stand with feet together. Measure around the widest part of the buttocks/hips.
Body Fat Percentage Categories (Ace Standard)
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2-5% | 10-13% |
| Athletes | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Obese | 25%+ | 32%+ |
Related Health Calculators
Body fat percentage is just one piece of the health puzzle. These related tools can help you build a complete health profile:
BMI Calculator →
Calculate Body Mass Index as a complementary screening tool for weight status
Ideal Weight Calculator →
Determine your ideal weight range based on multiple factors including body composition
BMR Calculator →
Calculate Basal Metabolic Rate to understand your calorie needs based on body composition
TDEE Calculator →
Calculate Total Daily Energy Expenditure for effective weight management
Frequently Asked Questions
- Which body fat formula is more accurate: US Navy or RFM?
- Both have strengths. The US Navy Method is long-established and widely used, typically accurate within 3-4% of DEXA scans when measurements are precise. The Relative Fat Mass (RFM) formula is a newer (2018) method largely considered more accurate than BMI-based estimates and simpler than the Navy method as it relies mainly on height and waist ratio. Using both gives you a robust range.
- Why do I need to measure my neck for body fat?
- For the US Navy Method, neck circumference is crucial because it helps distinguish between muscle and fat. A thicker neck often correlates with higher lean body mass (muscle), allowing the formula to adjust the body fat percentage downward for muscular individuals.
- Why does measuring at different times give different results?
- Your waist size can fluctuate throughout the day due to hydration, food intake, and bloating. For the most consistent results, measure yourself first thing in the morning, after using the bathroom and before eating or drinking.
- What is the difference between "Essential Fat" and "Storage Fat"?
- Essential fat is the minimum amount of fat necessary for basic physical and physiological health (cushioning organs, hormone regulation). Storage fat is the accumulated fat in adipose tissue. Dropping below essential fat levels is dangerous to your health.