BMI Calculator

BMI (Body Mass Index) is a measure that uses your height and weight to assess whether your weight is healthy. Developed by Belgian mathematician Adolphe Quetelet in the 19th century, BMI is the most widely used method worldwide to classify weight status.

While BMI doesn't directly measure body fat, studies show a strong correlation between BMI and body fat percentage measured by more precise methods. It's a useful, quick, and free screening tool.

BMI Formula

BMI = Weight (kg) / Height² (m²)

For example, if you weigh 70 kg and are 1.75 m tall:

• BMI = 70 / (1.75 × 1.75)
• BMI = 70 / 3.06
• BMI = 22.9

WHO Classification

According to the World Health Organization (WHO):

Required Data

1. Weight - In kilograms (kg) or pounds (lb)
2. Height - In centimeters (cm), meters (m), or feet/inches

Steps to Calculate

1. Enter your weight

   • Example: 75 kg or 165 lb

2. Enter your height

   • Example: 170 cm, 1.70 m, or 5'7"

3. Get instant result

   • Your BMI
   • Weight classification
   • Health recommendations

Situation: María is 28 years old, weighs 68 kg, and is 1.62 m tall. She wants to know if her weight is healthy.

Step-by-step solution:

1. Data:

   • Weight = 68 kg
   • Height = 1.62 m

2. BMI Calculation:

   • BMI = 68 / (1.62 × 1.62)
   • BMI = 68 / 2.62
   • BMI = 25.9

3. Interpretation:

   • BMI of 25.9 falls in the "Overweight" range (25.0 - 29.9)
   • She is slightly above the normal range (18.5 - 24.9)

4. Recommendation:

   • To reach normal weight (BMI < 25), María should weigh less than 65.5 kg
   • Should lose approximately 2.5 kg to reach the upper limit of normal weight
   • Healthy loss rate: 0.5-1 kg per week
   • Estimated time: 3-5 weeks with proper diet and exercise

✅ Measure in the morning: Weight varies throughout the day. For consistency, measure yourself in the morning, fasted, after using the bathroom.

✅ BMI is a guide, not a diagnosis: It doesn't distinguish between muscle mass and fat. An athlete may have high BMI but low body fat.

✅ Consider your age: BMI interpretation can vary with age. Older adults may have slightly higher healthy BMI.

✅ Measure waist circumference: Men > 102 cm and women > 88 cm indicate increased health risk, even with normal BMI.

✅ Focus on trends, not one measurement: Track your BMI over time. One abnormal measurement doesn't define your health.

✅ Consult a professional: For detailed assessment, see a doctor or certified nutritionist who can consider additional factors.

Is BMI accurate for everyone?

No. BMI has limitations for:

• Athletes and muscular people: High muscle mass can elevate BMI without excess fat
• Elderly: May have normal BMI despite unhealthy fat-to-muscle ratio
• Children and teens: Require age and gender-specific growth charts
• Pregnant women: BMI doesn't apply during pregnancy
• Different ethnicities: Some populations have different BMI-risk relationships

What's the difference between BMI and body fat percentage?

BMI uses only weight and height. Body fat percentage specifically measures the proportion of fat in your body. Someone can have normal BMI but high body fat (%fat), or high BMI but low body fat (athletes).

How can I lower my BMI healthily?

1. Caloric deficit: Consume 10-20% fewer calories than you burn
2. Balanced nutrition: More vegetables, lean protein, whole grains
3. Regular exercise: 150+ minutes of moderate activity per week
4. Avoid crash diets: Lose 0.5-1 kg per week maximum
5. Sleep well: 7-9 hours nightly
6. Manage stress: Chronic stress promotes weight gain

Can I have normal BMI and still be unhealthy?

Yes. This is called "metabolically unhealthy normal weight" or "skinny fat." You can have normal BMI but high body fat percentage, poor diet, sedentary lifestyle, and metabolic issues like insulin resistance. Health is more than just BMI.

Why does a BMI calculator sometimes give different results?

Small differences can occur due to:

• Rounding of decimal places
• Imperial vs. metric unit conversions
• Different formulas (some adjust for age or gender) Our calculator uses the standard WHO formula for consistency.

What BMI should I aim for?

For most adults, aiming for a BMI between 20-25 is ideal. Within the normal range (18.5-24.9), being in the middle-to-lower end is associated with lowest health risks. However, consult your doctor for personalized goals.