Free tools
Stop guessing. Start measuring.
Every calculator on HealthNation is built on a peer-reviewed formula and shows you the math. Optionally email yourself the result alongside a personalized plan.
Composite & decision tools
HealthNation Score
A 0–100 composite of the nine highest-leverage health levers. Track it month-to-month.
Open tool →Biological age calculator
How old your body actually behaves. 10 questions, 2 minutes.
Open tool →Mental health self-screener
PHQ-9 + GAD-7 — the same validated tools clinicians use.
Open tool →Daily habit tracker
8 evidence-based habits, streaks saved in your browser. No signup.
Open tool →Symptom checker
Body-area picker → likely causes + when to call a doctor.
Open tool →Supplement stack builder
Pick your goals → an evidence-graded short stack. Honest about what to skip.
Open tool →GLP-1 readiness quiz
8 questions, 3 minutes. Find out whether a GLP-1 might fit your situation.
Open tool →
Single-purpose calculators
BMR calculator
Basal metabolic rate using the Mifflin–St Jeor equation.
Open tool →Protein calculator
How much protein you actually need per day, based on body weight + activity.
Open tool →Sleep debt calculator
How much sleep you owe yourself — and how long it takes to repay it.
Open tool →VO₂ max estimator
Cardiorespiratory fitness from a sub-max test or wearable data.
Open tool →Hydration calculator
Daily water needs given your weight, climate, and activity.
Open tool →Macro calculator
Protein, fat, carb targets given your goal and energy needs.
Open tool →Body fat % calculator
US Navy circumference method, validated to ±3%. No calipers needed.
Open tool →Heart rate zones
Karvonen formula — 5 personal training zones, recovery to VO₂ max.
Open tool →Calorie burn calculator
50+ activities × time × weight, using validated MET values.
Open tool →Ideal weight calculator
Five classic formulas side-by-side, plus the healthy BMI window.
Open tool →Pregnancy due date
LMP, conception, or IVF transfer. Weekly milestones included.
Open tool →7-day meal plan generator
Custom calorie target + diet style. Full week + grocery list.
Open tool →