Health Calculators
Evidence-based health calculators built for nurses, dietitians, coaches, and self-trackers. Compute BMI against WHO classifications, dial in calories with the Mifflin-St Jeor equation, and translate every number into actionable ranges - no sign-up, no paywall, just clean formulas grounded in CDC, WHO, and ACSM guidance.
All Health Calculators
Tap a tool below to start. Every page shows the formula, an interactive widget, and a results explanation grounded in published clinical or sports-science references.
BMI Calculator
Body Mass Index with WHO-classified weight categories, healthy-range bands, and metric/imperial inputs for adults and athletes.
BMI = kg / m²Calorie Calculator
Daily calorie needs from Mifflin-St Jeor BMR + activity multiplier, with maintenance, cut, and bulk targets for evidence-based dieting.
TDEE = BMR × Activity FactorWHO BMI Classification
Adult cut-offs used across our calculators. Source: World Health Organization Technical Report Series 854 and 894.
| Category | BMI (kg/m²) | Risk of comorbidity |
|---|---|---|
| Underweight | < 18.5 | Low (other clinical issues) |
| Healthy range | 18.5 - 24.9 | Average |
| Overweight | 25.0 - 29.9 | Increased |
| Obese class I | 30.0 - 34.9 | Moderate |
| Obese class II | 35.0 - 39.9 | Severe |
| Obese class III | ≥ 40.0 | Very severe |
TDEE Activity Multipliers
Mifflin-St Jeor BMR × activity factor = TDEE. Adjust by ±500 kcal for cut or bulk goals.
| Activity level | Factor | Description |
|---|---|---|
| Sedentary | 1.20 | Desk job, little exercise |
| Lightly active | 1.375 | Light exercise 1-3 days/week |
| Moderately active | 1.55 | Moderate exercise 3-5 days/week |
| Very active | 1.725 | Hard exercise 6-7 days/week |
| Extra active | 1.90 | Physical job + 2-a-day training |
Related Calculator Categories
Why this calculator category exists
In 2026, a registered dietitian planning a 12-week weight-loss arc needs to (a) confirm a client's BMI against WHO cut-offs, (b) compute the Mifflin-St Jeor BMR, and (c) subtract a 500-kcal deficit from TDEE - without bouncing between three websites and a paid clinical app. Cardiac nurses doing post-op discharge education have the same workflow. So do strength coaches programming hypertrophy phases.
These calculators package the formulas that practitioners use daily into one fast, private, free index. We cite the original studies (Mifflin et al. 1990, WHO TRS 894, ACSM 11th edition) so you can take the printout to a provider visit with confidence.
What Health Pros Say
“Reliable BMI and calorie tools I trust to share with patients during discharge planning. The WHO ranges are clearly labelled and the unit toggle works perfectly for our international post-op cases.”
“I use the calorie calculator in every initial intake. The Mifflin-St Jeor + activity multiplier matches my clinical software within 30 calories, and patients can re-run it at home for free.”
“Athletes get confused when BMI flags them as overweight - this site explains the muscle caveat right on the page. The TDEE bulk/cut targets are spot on for off-season programming.”
“I print these for patients who want to track at home. No paywall, no upsell, just the formulas with proper citations - exactly what a clinic handout should be.”
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