BMI Calculator: How to Calculate and Understand Your BMI
What is BMI?
Body Mass Index (BMI) is a simple calculation using a person's height and weight. It's used as a screening tool to identify whether a person is underweight, at a healthy weight, overweight, or obese.
BMI Formula
Metric Formula
Imperial Formula
How to Calculate Your BMI
Step-by-Step (Metric)
- Measure your weight in kilograms
- Measure your height in meters
- Square your height (multiply it by itself)
- Divide your weight by your height squared
Example Calculation
For a person who weighs 70 kg and is 1.75 m tall:
- Height² = 1.75 × 1.75 = 3.0625
- BMI = 70 Ă· 3.0625 = 22.86
- Result: BMI of 22.9 (Normal weight)
BMI Categories
Standard BMI Ranges (Adults)
- Underweight: BMI less than 18.5
- Normal weight: BMI 18.5 - 24.9
- Overweight: BMI 25 - 29.9
- Obese (Class I): BMI 30 - 34.9
- Obese (Class II): BMI 35 - 39.9
- Obese (Class III): BMI 40 or higher
BMI Chart by Height and Weight
For Height 5'5" (165 cm)
- Underweight: Less than 111 lbs (50 kg)
- Normal: 111-149 lbs (50-68 kg)
- Overweight: 150-179 lbs (68-81 kg)
- Obese: 180+ lbs (82+ kg)
For Height 5'9" (175 cm)
- Underweight: Less than 125 lbs (57 kg)
- Normal: 125-168 lbs (57-76 kg)
- Overweight: 169-202 lbs (77-92 kg)
- Obese: 203+ lbs (92+ kg)
For Height 6'0" (183 cm)
- Underweight: Less than 136 lbs (62 kg)
- Normal: 136-184 lbs (62-83 kg)
Normal Weight (BMI 18.5-24.9)
Indicates:
- Healthy weight range for your height
- Lower risk of weight-related diseases
- Maintain through balanced diet and exercise
Overweight (BMI 25-29.9)
May indicate:
- Increased health risks
- Consider lifestyle changes
- Focus on nutrition and physical activity
Obese (BMI ≥ 30)
Indicates:
- Significantly increased health risks
- Consult healthcare provider
- May need medical intervention
Limitations of BMI
BMI Doesn't Account For:
- Muscle mass: Athletes may have high BMI but low body fat
- Bone density: Varies by individual
- Age: Older adults may have different healthy ranges
- Sex: Men and women carry fat differently
- Ethnicity: Different populations have different risk factors
Who Should Use Caution with BMI?
- Athletes and bodybuilders
- Pregnant or breastfeeding women
- Children and teenagers (use age-specific charts)
- Elderly individuals
Better Health Indicators
Additional Measurements
- Waist circumference: Measures abdominal fat
- Waist-to-hip ratio: Fat distribution indicator
- Body fat percentage: More accurate than BMI
- Muscle mass: Important for overall health
Healthy Waist Circumference
- Men: Less than 40 inches (102 cm)
- Women: Less than 35 inches (88 cm)
Achieving a Healthy BMI
Healthy Weight Loss Tips
- Set realistic goals: 1-2 lbs per week
- Balanced diet: Focus on whole foods
- Regular exercise: 150 minutes per week
- Track progress: Monitor weight and measurements
- Stay hydrated: Drink plenty of water
- Get enough sleep: 7-9 hours per night
Healthy Weight Gain Tips
- Eat more frequent meals
- Choose nutrient-dense foods
- Add healthy fats and proteins
- Strength training exercises
- Consult a nutritionist
BMI for Children and Teens
Children's BMI is calculated the same way, but interpreted differently using age and sex-specific percentile charts:
- Underweight: Less than 5th percentile
- Healthy weight: 5th to 85th percentile
- Overweight: 85th to 95th percentile
- Obese: 95th percentile or higher
When to See a Doctor
Consult a healthcare provider if:
- Your BMI is outside the normal range
- You have rapid weight changes
- You have weight-related health concerns
- You need help with weight management
- You have eating disorder symptoms
Conclusion
BMI is a useful screening tool for assessing whether your weight is in a healthy range for your height. However, it's just one indicator of health and should be considered alongside other factors like diet, exercise, body composition, and overall wellness.
For quick weight and height conversions to calculate your BMI, use our Weight Converter and Length Converter tools!