Body Fat & Resting Energy Estimator
Enter tape measurements for a historical Navy-derived body-fat estimate and an adult Mifflin–St Jeor resting-energy estimate. The outputs are screening-style estimates, not diagnoses, official Navy BCA results, measured energy expenditure, or diet targets.
Measurements
All anthropometric fields start blank. Nothing is calculated until you select Calculate estimates.
Results
Complete the form and select Calculate estimates. No personalized result is shown before you submit.
What the circumference equation does
Hodgdon and Beckett developed the original male and female equations at the Naval Health Research Center in 1984. They used tape circumferences and height to predict body density or body fat in Navy personnel. The criterion method was underwater weighing, with the Siri conversion used where density was converted to percent fat. That research history does not make an individual's estimate equivalent to DXA or another laboratory measurement.
| Coefficients | Equation |
|---|---|
| Male | % fat = 86.010 × log(waist − neck) − 70.041 × log(height) + 36.76 |
| Female | % fat = 163.205 × log(waist + hip − neck) − 97.684 × log(height) − 78.387 |
Primary and official context: the National Academies' account of the 1984 Hodgdon–Beckett Navy reports, the National Academies' publication of the continuous DoD circumference equations, and the Navy's current Guide 4: Body Composition Assessment (June 2026).
What the energy equation does
Mifflin, St Jeor, and colleagues derived a resting energy expenditure equation from 498 healthy adults ages 19–78 whose REE was measured by indirect calorimetry. The simplified equations used here are:
- Male coefficients: REE = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
- Female coefficients: REE = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Source: Mifflin MD, St Jeor ST, Hill LA, et al. (1990), “A new predictive equation for resting energy expenditure in healthy individuals”. The optional activity factors are practical approximations added by this calculator; they were not validated in that paper. No deficit or diet target is applied.
When not to lean on the estimate
Regression equations work best when the person and measurement protocol resemble the data used to build them. The original Navy sample was not stratified to mirror all Navy demographics. A National Academies review also found that the Navy equation could overestimate fatness in some strong women. Very muscular or lean bodies and unusual proportions therefore deserve particular caution.
Pregnancy changes body shape, fluids, and tissue composition; edema or ascites can also change circumferences without representing body fat. The Navy's current pregnancy policy defers official PFA participation during pregnancy and for 12 months afterward. Use clinical guidance rather than this calculator for pregnancy, substantial swelling, or a condition that changes fluid balance.
Supporting context: the National Academies' review of military body-composition methods and muscularity, its review of body-composition assumptions in pregnancy, a peer-reviewed review of edema and circumference measurement, and the Navy's Guide 8: Managing PFA Records for Pregnant Sailors (June 2026).
A repeatable tape measurement
- Use a flexible, non-stretch tape on bare skin.
- Keep the tape horizontal and snug without compressing tissue.
- Stand normally; do not pull in the abdomen.
- Repeat each site. If repeats differ, remeasure before entering a value.
If you are completing an official Navy BCA, ignore this summary and follow the current Guide 4 procedures exactly.
Frequently asked questions
Is this the current official U.S. Navy BCA calculation?
No. This page calculates a continuous research equation descended from the 1984 Hodgdon–Beckett circumference work. The Navy's June 2026 Guide 4 uses its own measurement, rounding, screening, table, and PRIMS procedures based on height, waist, and weight. Use the current guide and authorized Navy process for an official result.
How accurate is the circumference estimate?
It is a regression estimate, not a direct measurement of body fat. The original Navy equations were developed against body density from underwater weighing in Navy personnel. Tape placement, body proportions, and differences from that development sample can shift an individual's result. It is not interchangeable with DXA or another laboratory method.
Why are there male and female coefficient sets?
The source research published separate equations from groups classified as male or female and did not validate one coefficient set for every body type or hormonal context. The selection is a modeling input, not a statement about gender identity. If neither set fits the protocol you need, do not rely on this estimate.
When can a tape-based estimate be less useful?
Pregnancy changes body shape and tissue composition, and edema or ascites can change circumferences. Unusual body proportions and very muscular or very lean builds can also reduce the usefulness of an equation derived in a different population. Ask a clinician which assessment, if any, fits your situation.
What do the energy numbers mean?
The Mifflin–St Jeor equation predicts resting energy expenditure from weight, height, age, and a male or female coefficient. An optional activity multiplier gives a rough scenario, not measured expenditure, maintenance calories, a keto target, or a weight-loss prescription.
Are my measurements saved?
No. This calculator keeps entries only in the page's temporary memory while it is open. It does not save them to local storage or an account.