BMI Calculator
Calculate your Body Mass Index (BMI) to assess if you're at a healthy weight. Includes BMI categories and health recommendations.
Understanding BMI (Body Mass Index)
BMI is a simple calculation using height and weight to estimate body fat. While imperfect, it's widely used by healthcare providers as a quick screening tool for weight categories that may lead to health problems. Developed in the 1800s, BMI remains relevant today as an initial assessment tool.
BMI Categories
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5-24.9
- Overweight: BMI 25-29.9
- Obese (Class 1): BMI 30-34.9
- Obese (Class 2): BMI 35-39.9
- Obese (Class 3): BMI 40+
BMI Formula
Imperial: BMI = (weight in pounds / (height in inches)²) × 703
Metric: BMI = weight in kg / (height in meters)²
Health Implications
BMI 18.5-24.9 (Normal Weight)
Associated with lowest risk of weight-related health issues. Maintain through balanced diet and regular exercise.
BMI Below 18.5 (Underweight)
May indicate malnutrition, eating disorder, or underlying health condition. Can lead to weakened immune system, osteoporosis, anemia, fertility issues.
BMI 25-29.9 (Overweight)
Increased risk of: type 2 diabetes, high blood pressure, heart disease, stroke, certain cancers. Losing 5-10% of body weight can significantly improve health markers.
BMI 30+ (Obese)
Significantly increased risk of serious health conditions. Benefits greatly from weight loss through diet, exercise, and potentially medical intervention.
BMI Limitations
- Doesn't measure body fat directly: Can't distinguish between muscle and fat
- Athletes/Bodybuilders: High muscle mass = high BMI but low body fat
- Elderly: May have normal BMI but reduced muscle mass
- Ethnicity: Health risks vary by ethnicity at same BMI
- Gender: Women naturally have more body fat than men
- Children/Teens: Require age and sex-specific BMI percentiles
Better Alternatives
Body Fat Percentage
More accurate measure of fitness:
- Men: 10-20% healthy, 20-25% average, 25%+ overweight
- Women: 20-30% healthy, 30-35% average, 35%+ overweight
Waist Circumference
Predicts disease risk independent of BMI:
- Men: Over 40 inches = increased risk
- Women: Over 35 inches = increased risk
Waist-to-Hip Ratio
Measures fat distribution:
- Men: Under 0.90 healthy
- Women: Under 0.85 healthy
BMI Examples
5'4" (64 inches):
- 110 lbs = BMI 18.9 (Normal)
- 130 lbs = BMI 22.3 (Normal)
- 150 lbs = BMI 25.7 (Overweight)
- 180 lbs = BMI 30.9 (Obese)
5'10" (70 inches):
- 130 lbs = BMI 18.6 (Normal)
- 160 lbs = BMI 23.0 (Normal)
- 180 lbs = BMI 25.8 (Overweight)
- 210 lbs = BMI 30.1 (Obese)
Healthy Weight Loss
Safe rate: 1-2 lbs per week
To lose 1 lb/week: Create 500 calorie deficit daily (3,500 per week)
- Reduce calorie intake by 250
- Increase exercise to burn 250
- Total: 500 calorie daily deficit
Tips for Healthy BMI
- Balanced diet: Fruits, vegetables, whole grains, lean protein
- Portion control: Use smaller plates, measure servings
- Regular exercise: 150 minutes moderate activity weekly
- Strength training: Builds muscle, increases metabolism
- Adequate sleep: 7-9 hours per night
- Manage stress: Reduces cortisol and emotional eating
- Stay hydrated: Drink water throughout day
- Limit processed foods: Reduce sugar, salt, unhealthy fats
When to Consult a Doctor
- BMI below 18.5 or above 30
- Rapid unexplained weight change
- Weight affecting daily activities
- Considering weight loss medication or surgery
- Health conditions like diabetes or heart disease
Health Tip: Don't obsess over BMI number. It's one metric among many. Focus on how you feel, your energy levels, fitness abilities, and overall health markers (blood pressure, cholesterol, blood sugar). A sustainable healthy lifestyle matters more than any single number!