Cunningham TDEE calculator

The path is pure arithmetic with no network and no random seed, so coaching apps, homework checkers, and prepaid API clients get identical JSON every time. Non-positive lean mass and invalid activity inputs fail with invalid_input and are not billed.

What Cunningham measures and which inputs you need

Basal metabolic rate is the energy your body would spend at complete rest over twenty-four hours. Total daily energy expenditure adds the cost of daily movement and training through a multiplier called the activity factor. Cunningham starts from lean body mass—also called fat-free mass—rather than from total weight, age, height, or sex, so the resting baseline tracks metabolically active tissue. Send lean_mass as a positive finite number in kilograms; aliases lean_mass_kg, lbm, fat_free_mass, ffm, and lean_body_mass are accepted. Provide activity as one of sedentary, light, moderate, active, or very_active, which map to the classic multipliers one point two, one point three seven five, one point five five, one point seven two five, and one point nine. Alternatively send activity_factor as a positive finite number when your protocol uses a custom multiplier; when both are present the numeric factor wins. The engine computes bmr_kcal_day as five hundred plus twenty-two times lean mass, then tdee_kcal_day as BMR times the resolved factor. Missing fields, non-finite numbers, non-positive lean mass, and unrecognised activity labels fail validation with invalid_input. Identical inputs always yield identical JSON because the algorithm never touches the network, a model, a clock, or a random generator.

Reading the response fields and common pitfalls

On success the response echoes lean_mass_kg and activity_factor, reports bmr_kcal_day and tdee_kcal_day in kilocalories per day, and sets unit to kcal/day so UIs can label the numbers without hard-coding strings. Use bmr_kcal_day when a clinician or coach wants the resting baseline alone; use tdee_kcal_day as the maintenance calorie target before applying a surplus or deficit in your own product. Do not confuse this endpoint with Mifflin-St Jeor or Katch-McArdle: the constants five hundred and twenty-two are specific to Cunningham on fat-free mass.

API usage, pricing, coaching workflows, and practical limits

Call the free in-browser Cunningham TDEE calculator for quick checks, lecture demos, and client education without installing a nutrition spreadsheet. Prefer kilogram lean-mass inputs that match the published constants; if your UI collects pounds, convert before calling. Keep expectations clinical: this is an educational and planning estimate, not a diagnostic medical device, and users with atypical body composition or medical conditions should follow professional advice rather than any single formula alone. Send a JSON body with required lean_mass and either activity or activity_factor (or their aliases). Use the prepaid API when a fitness SaaS, telehealth intake form, sports-science lab notebook, or calorie-planning pipeline needs a stable contract under KIT balance at $0.002 per successful item; validation failures never consume balance after the engine rejects the request. Pair this endpoint with a body-composition workflow on the client side that already stores lean mass, then store BMR and TDEE in your own database for longitudinal charts as composition and activity change. Authors shipping SDKs can map tdee_kcal_day directly into dashboards and export CSV columns labeled lean mass, basal calories, and maintenance calories—the same numbers coaches write by hand when they apply Cunningham on paper.