Relative Fat Mass (RFM) Calculator
RFM estimates body fat percentage using only height and waist circumference. It often tracks body composition better than BMI, especially when muscle mass varies.
Enter Your Measurements
Use a soft tape measure. Keep it level and snug, but not tight, around the waist.
Your RFM Results
Relative Fat Mass
24.0%
Waist-to-Height Ratio
0.50
Interpretation
Overfat range. Consider lifestyle adjustments.
How to Use This Calculator
Take precise measurements
Measure height without shoes and waist at the midpoint between the lowest rib and the top of the hip bone.
Compare RFM to other metrics
Use RFM alongside BMI, waist-to-height ratio, and body fat tests to get a complete view of your body composition.
Track progress
Repeat measurements monthly to monitor changes from nutrition or training plans.
Formula
RFM = 64 − 20 × (Height ÷ Waist) + 12 × Sex
- Use meters for both height and waist before applying the formula.
- Sex is 0 for males and 1 for females (adding 12% for females).
- Waist-to-height ratio = Waist (cm) ÷ Height (cm).
Example: Male, height 1.80 m, waist 0.90 m → RFM = 64 − 20 × (1.80 ÷ 0.90) = 24%.
Why Use RFM?
Relative Fat Mass uses waist measurements to capture abdominal adiposity, a strong predictor of metabolic risk. Research shows it can outperform BMI when estimating body fat percentage in diverse populations.
Combine RFM with strength assessments, nutrition tracking, and medical checkups to build a complete health plan.
Frequently Asked Questions
Do I need to fast before measuring?
No. For consistency, measure at the same time of day, preferably in the morning before meals.
Is RFM accurate for athletes?
RFM performs better than BMI for muscular individuals, but DEXA or other body composition tests provide the most precise data.
What if my waist circumference fluctuates?
Waist can vary with meals or hydration. Take multiple measurements across days and average them for reliable trends.
Can children use this calculator?
The adult RFM formula is validated for adults. Children and teens require age-specific metrics.