BMI Calculator

You can also use Percentage Calculator

What This Tool Does

This calculator takes your height and weight and returns your Body Mass Index — a number used to indicate whether your weight is in a healthy range for your height. It works for both metric inputs (kg and cm) and imperial inputs (lbs and feet/inches), and covers adults as well as children and teens. Alongside BMI, it also computes your BMI Prime and Ponderal Index, both explained below.

How BMI Is Calculated

BMI divides your weight by the square of your height.

Metric formula:
BMI = weight (kg) ÷ height² (m)

Imperial formula:
BMI = 703 × weight (lbs) ÷ height² (inches)

Worked Example:

A person who is 5’10” (177.8 cm) and weighs 160 lbs (72.57 kg):

• Metric: 72.57 ÷ 1.778² = 23.0
• Imperial: 703 × 160 ÷ 70² = 23.0

Both formulas give the same result — choose whichever unit system you’re comfortable with.

BMI Categories for Adults

The World Health Organization uses the following ranges for adults aged 20 and above. The same scale applies to both men and women.

Classification	BMI (kg/m²)
Severe Thinness	Below 16
Moderate Thinness	16 – 17
Mild Thinness	17 – 18.5
Normal	18.5 – 25
Overweight	25 – 30
Obese Class I	30 – 35
Obese Class II	35 – 40
Obese Class III	Above 40

BMI Categories for Children and Teens

For anyone aged 2 to 20, the CDC uses percentile ranges rather than fixed BMI values, since body composition changes significantly during growth years.

Category	Percentile Range
Underweight	Below 5th
Healthy Weight	5th – 85th
At Risk of Overweight	85th – 95th
Overweight	Above 95th

Risks of Being Overweight

Carrying excess weight over time raises the risk of several serious health conditions, including high blood pressure, high LDL cholesterol, Type II diabetes, coronary heart disease, stroke, sleep apnea, and certain cancers. There is also a generally increased risk of mortality compared to those in the normal BMI range. A BMI consistently above 25 is worth discussing with a doctor, even if no symptoms are present.

Risks of Being Underweight

Low body weight carries its own set of health risks. These include malnutrition, vitamin deficiencies, weakened bones (osteoporosis), reduced immune function, and growth issues in younger individuals. For women, being underweight can disrupt hormonal balance and affect reproductive health. If low weight is unexplained or persistent, a medical consultation is advisable.

Limitations of BMI

BMI is a useful screening tool but not a complete picture of health. It measures total body weight relative to height — it cannot distinguish between fat, muscle, and bone mass.

A few important considerations:

• Older adults tend to carry more body fat than younger adults at the same BMI
• Women generally have a higher body fat percentage than men at the same BMI
• Athletes and bodybuilders may register as overweight due to high muscle mass, even when body fat is low
• Children and teens are better assessed using age- and sex-specific percentile charts rather than adult BMI ranges

BMI works well as an initial indicator for large populations, but individual assessments benefit from additional measurements like waist circumference or body fat percentage.

BMI Prime

BMI Prime is your BMI expressed as a ratio against the upper limit of the normal range (25 kg/m²).

Formula: BMI Prime = BMI ÷ 25

A BMI Prime below 1 means you’re within or below the normal range. Above 1 means overweight; above 1.2 means obese. It’s a quick way to see how far your BMI sits from the normal ceiling without needing to read a table.

Ponderal Index

The Ponderal Index (PI) is similar to BMI but cubes the height instead of squaring it. This makes it more reliable for people at the extreme ends of the height spectrum — very tall or very short individuals — where BMI tends to overestimate or underestimate body fat.

Metric formula: PI = weight (kg) ÷ height³ (m)

Imperial formula: PI = height (inches) ÷ ∛weight (lbs)

For the same 5’10”, 160 lb example: PI = 70 ÷ ∛160 = 12.9

Who Uses This

• Adults checking whether their current weight sits within a healthy range
• Men and women in India tracking weight in kg and cm for health or fitness goals
• Parents monitoring growth patterns for children and teenagers
• Fitness enthusiasts using BMI alongside other metrics like body fat percentage
• Anyone preparing for a medical check-up who wants a baseline number before their appointment

FAQ

Is BMI different for men and women?

The formula is the same, but body composition differs — women naturally carry more body fat than men at the same BMI. This is one of BMI’s known limitations as a universal measure.

Which BMI range is considered healthy in India?

The standard WHO range of 18.5 to 25 is widely used in India. Some research suggests Asian populations may face health risks at lower BMI thresholds, so it’s worth discussing this with a doctor for a personalised assessment.

Can I use this BMI calculator for kids?

Yes, but interpret results differently. For ages 2 to 20, BMI is assessed using age- and sex-specific percentile charts rather than the adult category table above.

Does BMI account for age?

The adult BMI formula does not adjust for age, though older adults typically carry more body fat at the same BMI than younger adults. The children’s BMI chart does factor in age and sex.

What is a healthy BMI for my height and weight in kg?

Enter your weight in kg and height in cm above — the calculator will return your BMI and the corresponding category. A result between 18.5 and 25 is considered normal for adults.

A Note on Results

BMI is a general screening indicator, not a medical diagnosis. Use this result as a starting point, not a final verdict on your health. If your BMI falls outside the normal range, consider speaking with a healthcare professional before making changes to your diet or exercise routine.