Health
Body Metrics Calculator
Compare formula-based estimates of body composition, resting energy and reference weight.
Body Metrics Calculator
Results are mathematical estimates, not measurements or diagnoses.
Some equations were developed with different coefficients for male and female study groups.
Enter a positive waist circumference.
Result
Body composition
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Body Metrics Calculator
RFM uses height, waist and formula sex; Deurenberg uses BMI, age and formula sex; Hodgdon-Beckett uses defined circumferences.
Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle estimate basal/resting energy, not total energy needs.
WHtR relates waist to height. FFMI standardizes estimated fat-free mass for height.
Actual body fat requires measurement; indirect calorimetry can measure resting energy.
Devine, Robinson and Lemmens are historical formula references, not target weights.
BMI is only a helper for Deurenberg. Use the BMI Calculator for classic BMI categories.
Results are mathematical estimates, not measurements or diagnoses.
FAQ
Why do body-fat methods differ?
They use different inputs, study groups and models.
Is fat-free mass muscle mass?
No. It also includes water, bone, organs and other fat-free components.
What is WHtR?
The dimensionless ratio of waist circumference to height in the same unit.
Is WHtR a diagnosis?
No. FreeTools only shows the mathematical ratio.
What is FFMI?
FFMI divides fat-free mass in kilograms by squared height in metres.
Is FFMI a muscle index?
No. It is based on all fat-free mass, not muscle alone.
Why does FFMI depend on my body-fat estimate?
FFM is derived from weight and the selected body-fat value, so its uncertainty carries into FFMI.
What is Katch-McArdle?
An FFM-based resting-energy estimate using 370 + 21.6 × FFM in kg.
Why do resting-energy formulas differ?
They use different inputs and were developed from different datasets.
Is reference weight my healthy target?
No. It is only a historical formula-based reference.