What does the Female Athlete Formula Suite calculate?

Methodology for the Female Athlete Formula Suite: women-specific FFMI, BMR, max HR, and body-fat corrections, plus menstrual-cycle category caveats.

What inputs does the Female Athlete Formula Suite require?

It takes the following inputs: weight kg, height cm, age, body fat pct, category.

What does the Female Athlete Formula Suite return?

It returns: ffmi, ffmiCeiling, bmrKcal, estimatedVo2Max, maxHeartRate, bodyFatPctEstimated, bmi, caveats.

Is the Female Athlete Formula Suite free to use?

Yes. It runs entirely client-side in your browser with no signup, and is also importable as an ES module engine for AI agents.

What category does the Female Athlete Formula Suite belong to?

Body Composition. See the methodology above for formulas, assumptions, and limitations.

Methodology: Female Athlete Formula Suite

Scope

Computes four standard performance / body-composition metrics with female-specific corrections, and surfaces phase-aware caveats for amenorrhea (RED-S concern), perimenopause, and postmenopause categories.

Formula

FFMI: Lean mass / height² (kg/m²). Drug-free female ceiling ≈ 22 (vs ~25 men) per Kouri 1995.
BMR (Mifflin-St Jeor): 10×kg + 6.25×cm − 5×age − 161 (female sex constant).
Max heart rate: 206 − 0.88×age (Gulati 2010 women-specific, more accurate than Tanaka general).
Body fat from BMI (Deurenberg): 1.20×BMI + 0.23×age − 5.4 (female intercept).
VO2-max age-prediction: Female baseline ~33 ml/kg/min for 30-yr-old, declining 0.5 ml/kg/min/yr (Fleg 2005).

Coefficients

Formula	Female-specific value	Note
FFMI ceiling	22	Kouri 1995 (n=157) drug-free band
Mifflin sex constant	−161	vs +5 male
Max HR slope	−0.88	Gulati 2010, women-specific
Deurenberg BMI intercept	−5.4	vs −10.8 male

Data sources

Kouri EM, Pope HG Jr, Katz DL, Oliva P. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med. 1995;5(4):223-228. — Drug-free FFMI distribution; female ceiling around 22.
Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247. — PMID 2305711. Source of the −161 female sex constant.
Gulati M, Shaw LJ, Thisted RA, Black HR, Bairey Merz CN, Arnsdorf MF. Heart rate response to exercise stress testing in asymptomatic women: the St. James Women Take Heart Project. Circulation. 2010;122(2):130-137. — PMID 20585015. Women-specific 206 − 0.88×age max HR.
Sims ST, Yeager S. ROAR: How to Match Your Food and Fitness to Your Female Physiology. Rodale Books; 2016. — Practical menstrual-cycle and perimenopause performance considerations.
Mountjoy M, Sundgot-Borgen J, Burke L, et al. IOC consensus statement: Relative Energy Deficiency in Sport (RED-S). Br J Sports Med. 2018;52(11):687-697. — RED-S syndrome reference for amenorrhea caveat.

Assumptions

Body fat % entered manually is reliable (DEXA / hydrostatic). Otherwise Deurenberg BMI-derived estimate is used.
Menstrual category is a self-report — the tool can't validate.
Athletes outside age 14–80 are out of validation range for several formulas.

Approximation range

FFMI ±1 unit (height-squared sensitivity is high). BMR ±150 kcal. Max HR ±8 bpm individual variance. Deurenberg-derived body fat ±3% absolute.

Limitations

Doesn't model menstrual-phase metabolic cost differences (~5% luteal vs follicular).
Doesn't replace clinical RED-S screening — referral to a sports physician is appropriate when amenorrhea is selected.
The "female athlete" framing is binary biological-sex by formula constraint; intersex / trans athletes need an individualised assessment.

Reproducibility

65 kg, 168 cm, 30 yr, 24% body fat: lean mass = 65 × 0.76 = 49.4 kg. FFMI = 49.4 / 1.68² = 17.5. BMR = 10×65 + 6.25×168 − 5×30 − 161 = 1389 kcal. Max HR = 206 − 0.88×30 = 179.6 bpm.

Change log

2026-05-08: methodology page first published.

FFMI Calculator — General FFMI without female-specific framing.
BMR Calculator — General Mifflin-St Jeor BMR.
Heart Rate Zone Calculator — Training zones from max HR.

Worked example

Computed by the same engine bundle served at /engines/female-athlete-formula-suite.js. Re-runnable: the values below are the literal output of compute(engineInput).

Input

tool: female_athlete_formula_suite
weight_kg: 65
height_cm: 168
age: 30
body_fat_pct: 24
category: regular_cycle

Output

ffmi: 17.5
ffmiCeiling: 22
bmrKcal: 1389
estimatedVo2Max: 33
maxHeartRate: 180
bodyFatPctEstimated: 24
bmi: 23
caveats: ["FFMI ceiling for natural female lifters: ~22 (Kouri 1995, n=157).","Mifflin-St Jeor uses the −161 female sex constant verbatim.","Max HR uses Gulati 2010 women-specific formula (206 − 0.88×age) for better accuracy than Tanaka."]

FAQ

What does the Female Athlete Formula Suite calculate?: Methodology for the Female Athlete Formula Suite: women-specific FFMI, BMR, max HR, and body-fat corrections, plus menstrual-cycle category caveats.
What inputs does the Female Athlete Formula Suite require?: It takes the following inputs: weight kg, height cm, age, body fat pct, category.
What does the Female Athlete Formula Suite return?: It returns: ffmi, ffmiCeiling, bmrKcal, estimatedVo2Max, maxHeartRate, bodyFatPctEstimated, bmi, caveats.
Is the Female Athlete Formula Suite free to use?: Yes. It runs entirely client-side in your browser with no signup, and is also importable as an ES module engine for AI agents.
What category does the Female Athlete Formula Suite belong to?: Body Composition. See the methodology above for formulas, assumptions, and limitations.