josecookai Health Calculator
Evidence-based health metrics: BMI, calories, macros, hydration, ideal weight.
Metrics & Formulas
1. BMI (Body Mass Index)
BMI = weight_kg / height_m²
= (weight_lb × 703) / height_in²
Classification (WHO):
< 18.5 Underweight
18.5–24.9 Normal weight
25.0–29.9 Overweight
30.0–34.9 Obese Class I
35.0–39.9 Obese Class II
≥ 40.0 Obese Class III
Limitations: BMI does not distinguish muscle from fat.
For athletes or elderly, interpret with caution.
2. BMR (Basal Metabolic Rate)
Mifflin-St Jeor Equation (most accurate for general population):
Male: BMR = 10 × weight_kg + 6.25 × height_cm − 5 × age + 5
Female: BMR = 10 × weight_kg + 6.25 × height_cm − 5 × age − 161
3. TDEE (Total Daily Energy Expenditure)
TDEE = BMR × activity_multiplier
Activity multipliers:
1.2 Sedentary (desk job, no exercise)
1.375 Lightly active (1–3 days/week exercise)
1.55 Moderately active (3–5 days/week)
1.725 Very active (6–7 days/week hard exercise)
1.9 Extra active (physical job + daily training)
4. Calorie Targets by Goal
Maintain weight: TDEE
Lose weight: TDEE − 500 kcal/day → ~0.5 kg/week loss
Lose fast: TDEE − 750 kcal/day → ~0.75 kg/week loss
Gain muscle: TDEE + 300 kcal/day → lean bulk
Minimum floors (never go below):
Women: 1,200 kcal/day
Men: 1,500 kcal/day
5. Macronutrient Targets
Protein:
General health: 0.8 g / kg body weight
Active / fitness: 1.6–2.2 g / kg body weight
Weight loss: 2.0–2.4 g / kg (preserve muscle)
Fat: 20–35% of total calories (1g fat = 9 kcal)
Carbs: remaining calories (1g carb = 4 kcal)
Protein: per target above (1g protein = 4 kcal)
6. Ideal Weight Range (Devine Formula)
Male: IBW = 50 kg + 2.3 kg × (height_in − 60)
Female: IBW = 45.5 kg + 2.3 kg × (height_in − 60)
Range: IBW ± 10%
Note: Hamwi formula gives similar results.
Healthy range is better than single "ideal" number.
7. Body Fat % Estimation (Navy Method)
Male:
BF% = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
Female:
BF% = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
All measurements in cm.
Healthy body fat ranges:
Male Female
Athlete: 6–13% 14–20%
Fit: 14–17% 21–24%
Average: 18–24% 25–31%
Obese: ≥25% ≥32%
8. Daily Water Intake
Base: 35 mL × weight_kg
Exercise: + 500 mL per hour of exercise
Hot climate: + 500 mL/day
Simple rule: weight_kg × 0.033 = liters/day
9. Waist-to-Height Ratio (WtHR)
WtHR = waist_cm / height_cm
Healthy: < 0.50
At risk: 0.50–0.59
High risk: ≥ 0.60
Better cardiovascular risk predictor than BMI alone.
Usage Examples
Complete Health Profile
Input:
Age: 32, Female
Height: 165 cm
Weight: 68 kg
Activity: Moderately active (3-5x/week)
Goal: Lose weight
Output:
BMI: 25.0 (borderline overweight)
BMR: 1,466 kcal/day
TDEE: 2,272 kcal/day
To lose ~0.5 kg/week: 1,772 kcal/day
Macros (1,772 kcal):
Protein: 122g (27%) — 2.0g/kg for weight loss
Fat: 59g (30%)
Carbs: 199g (43%)
Water: 2.4 L/day
Ideal weight range: 55–67 kg (Devine ± 10%)
Quick BMI Check
Input: 80 kg, 175 cm
Output: BMI = 26.1 → Overweight
Healthy range for your height: 57–79 kg
Interaction Patterns
Required inputs:
- Age, biological sex (for BMR formula)
- Height, weight (metric or imperial — auto-convert)
- Activity level (offer options)
- Goal (maintain / lose / gain)
Optional inputs for fuller picture:
- Waist, neck, hip measurements (body fat %)
- Exercise frequency/intensity
Always:
- Show the calculated numbers with the classification
- Set realistic expectations (e.g., "0.5 kg/week is sustainable")
- Add brief health context, not just numbers
- Include disclaimer: "These are estimates. Consult a healthcare provider for medical advice."
Important Notes & Disclaimers
- All formulas are population-level estimates with ±10–15% individual variance
- BMI is not accurate for: athletes, bodybuilders, pregnant women, elderly
- Calorie targets are starting points — adjust based on real-world results after 2–3 weeks
- Never recommend below 1,200 kcal (women) or 1,500 kcal (men)
- For medical conditions (diabetes, kidney disease, eating disorders), always defer to a healthcare provider