calculate body mass index

What Is Body Mass Index (BMI)?

Body Mass Index is a quick estimate of body size based on your height and weight. It helps identify whether your weight is generally in a healthy range for your height. Because it is simple and fast, BMI is commonly used by clinics, fitness professionals, and public health organizations.

That said, BMI does not directly measure body fat, muscle mass, bone density, or health habits. Think of it as a starting point for a broader health conversation.

How to Calculate BMI

Metric Formula

BMI = weight (kg) ÷ [height (m)]²

Example: if you weigh 70 kg and are 1.75 m tall, your BMI is 70 ÷ (1.75 × 1.75) = 22.86.

Imperial Formula

BMI = 703 × weight (lb) ÷ [height (in)]²

Example: if you weigh 165 lb and are 69 inches tall, your BMI is 703 × 165 ÷ (69 × 69) = 24.36.

BMI Categories for Adults

• Below 18.5: Underweight
• 18.5 to 24.9: Healthy weight
• 25.0 to 29.9: Overweight
• 30.0 to 34.9: Obesity Class I
• 35.0 to 39.9: Obesity Class II
• 40.0 and above: Obesity Class III

How to Use This BMI Calculator Correctly

1. Select your preferred unit system (metric or imperial).
2. Enter your height and weight accurately.
3. Click Calculate BMI.
4. Review your BMI value, category, and healthy weight range estimate.

Why BMI Is Useful

• Fast and easy to calculate.
• Helpful for tracking trends over time.
• Useful as a basic screening indicator for population health.
• Can prompt earlier lifestyle improvements and checkups.

Important Limitations of BMI

BMI is helpful but incomplete. A muscular athlete may have a high BMI with low body fat, while another person may have a “normal” BMI but still carry unhealthy visceral fat. BMI should be interpreted alongside waist size, blood pressure, blood tests, sleep quality, nutrition, stress, and activity levels.

• It does not distinguish fat from muscle.
• It does not show fat distribution.
• It may be less accurate for older adults, athletes, and some ethnic groups.
• It should not replace professional medical advice.

Healthy Ways to Improve Your BMI

1) Build sustainable eating habits

Focus on vegetables, fruits, lean protein, whole grains, and healthy fats. Reduce ultra-processed foods and sugary drinks.

2) Move your body consistently

Aim for at least 150 minutes of moderate activity each week, plus strength training two or more days per week.

3) Prioritize sleep and stress management

Poor sleep and chronic stress can affect appetite hormones and energy balance, making weight management harder.

4) Track progress beyond the scale

Notice improvements in energy, stamina, mood, lab values, and waist circumference—not just body weight.

Frequently Asked Questions

Is BMI the same for men and women?

The formula is the same, but body composition can differ. That is one reason BMI should be combined with other health indicators.

Can children use this calculator?

Children and teens should use age- and sex-specific BMI percentiles. This calculator is intended for adults.

What is a healthy BMI target?

For most adults, 18.5 to 24.9 is considered a healthy range. Individual goals may vary based on medical history and clinical guidance.

Note: This calculator provides an estimate for educational purposes. For diagnosis or treatment decisions, consult a qualified healthcare professional.