Body Fat Calculator

What this tool does

Body fat percentage estimates describe the share of body weight attributed to fat tissue. Field methods use anthropometry rather than imaging or densitometry.

DoseFirst offers validated educational equations only — not proprietary “black box” scoring. Results remain estimates.

What inputs are required

• Method selection: circumference (U.S. Navy / Hodgdon) or BMI-based (Deurenberg).
• Sex, as required by the equation.
• Circumference method: height plus neck and waist (and hip for females), measured carefully.
• BMI-based method: height, weight, age, and sex.

How the result is calculated

• Circumference methods use published logarithmic equations on height and girths.
• Deurenberg uses BMI, age, and sex in a published adult regression.
• Outputs are rounded percentage estimates for educational display.

What the result means

• Higher estimated percentages suggest a larger fat mass fraction relative to total weight.
• Population “healthy ranges” vary by age, sex, and reference source — this tool focuses on the estimate itself.
• Athletes and clinically supervised patients may fall outside general ranges for good reasons.

Important limitations

• Not equivalent to DXA, Bod Pod, hydrostatic weighing, or clinical labs.
• Tape placement error strongly affects circumference methods.
• Hydration, recent exercise, and menstrual cycle can shift short-term readings.
• Some body shapes and clinical conditions are poorly served by field equations.

When professional guidance may be useful

• Use clinical body-composition testing when decisions about therapy, surgery, or sports performance require precision.
• Discuss unexpected estimates with a clinician rather than making abrupt diet or training changes alone.