Relative Fat Mass (RFM) Calculator
Calculate Relative Fat Mass using the Woolcott-Bergman formula, a newer body fat estimation method that uses only height and waist circumference. RFM shows stronger correlation with DEXA-measured body fat than BMI.
Why This Health Metric Matters
Why: RFM improves obesity classification. No scale needed—just height and waist.
How: RFM = 64 - (20 × height/waist) for men; 76 - (20 × height/waist) for women.
- ●RFM Score
- ●Body Fat Estimate
- ●BMI Comparison
- ●Health Category
Sample Examples
RFM Health Assessment
Your RFM of 22.8% indicates Normal body fat. Health score: 100/100.
⚠️For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
🏥 Health Facts
r=0.86 accuracy vs DEXA
— Woolcott & Bergman 2018
Height and waist only
— Scientific Reports
What is RFM (Relative Fat Mass)?
RFM estimates body fat percentage from height and waist only. Published by Woolcott & Bergman in Scientific Reports (2018), it shows r=0.86 correlation with DEXA-measured body fat, outperforming BMI. No scale needed.
How Does RFM Work?
RFM = 64 - (20 × height/waist) + (12 × sex). For men: sex=0. For women: sex=1. Height and waist in same units (cm). The ratio reflects central adiposity.
How to Measure Waist
Measure at the narrowest point, usually just above the navel. Use a snug tape, not compressing the skin. Stand relaxed.
RFM vs BMI
RFM correlates 86% with DEXA vs 82% for BMI. RFM identifies central obesity and "skinny fat" better. No weight needed.
Healthy RFM Ranges
Men: 10-25% healthy. Women: 20-35% healthy. Very low or very high values warrant medical review.
When to Use RFM
Use RFM for health screening, body composition tracking, drug dosing estimates, and when BMI is misleading (e.g., athletes).
Clinical Applications
RFM is used for medication dosing, surgical risk, and nutritional planning. NIH and WHO guidelines support waist-based metrics.
Limitations
RFM is an estimate, not a substitute for DEXA or medical assessment. Pregnancy, edema, or ascites can affect accuracy.
FAQ
What is Relative Fat Mass (RFM)?
RFM estimates body fat percentage from height and waist circumference only. The Woolcott-Bergman formula (2018) shows r=0.86 correlation with DEXA-measured body fat, outperforming BMI.
How is RFM calculated?
RFM = 64 - (20 × height/waist) + (12 × sex). For men: sex=0. For women: sex=1. Height and waist in same units (cm). No scale needed.
Is RFM better than BMI?
Yes. RFM correlates with DEXA at r=0.86 vs BMI at r=0.82. RFM identifies central obesity better and requires no weight measurement.
What is a healthy RFM range?
Men: 10-25% healthy. Women: 20-35% healthy. Very low (<10% men, <20% women) or very high (>35% men, >45% women) warrant medical review.
Where do I measure waist for RFM?
Measure at the narrowest point, usually just above the navel. Use a snug tape snug but not compressing the skin.
Can RFM be used for drug dosing?
Yes. RFM is used clinically for medication dosing, surgical risk assessment, and nutritional planning due to its accuracy vs DEXA.