BMI Calculator

This BMI calculator helps you estimate your Body Mass Index using metric or imperial units. Enter your height and weight to see your BMI value, weight category, and healthy weight range for your height. Optional fields such as age, gender, and waist circumference provide context for your results.

Metric or Imperial: Choose between cm/kg or ft/in + lbs.
BMI value and category: See if you fall into underweight, normal, overweight, or obese ranges.
Healthy weight range: Suggested weight range based on your height.
Waist circumference check: Optional input to assess central obesity risk.
WHO standards: Uses World Health Organization BMI categories for accuracy.

How to use: Enter your height and weight in either metric or imperial units. The calculator will instantly display your BMI, category, and ideal weight range. Use waist measurement for additional health insights.

Common searches: BMI calculator online, healthy BMI range, BMI chart by age and gender, body mass index calculator metric and imperial.

Calculate your Body Mass Index (BMI) using metric or imperial units. See your BMI value, weight category, and ideal weight range for your height.

How the BMI calculator works

The BMI calculator measures weight in relation to height using the Body Mass Index formula. The result helps classify weight as underweight, normal, overweight, or obese, based on World Health Organization (WHO) standards.

Metric formula: BMI = weight (kg) ÷ height (m²)
Imperial formula: BMI = 703 × weight (lbs) ÷ height (in²)

BMI classification ranges

BMI results are grouped into categories that indicate weight status. These categories apply to adults of all ages, but may vary slightly in athletes and different ethnic groups.

Category	BMI Range
Underweight	< 18.5
Normal weight	18.5 – 24.9
Overweight	25 – 29.9
Obese (Class I)	30 – 34.9
Obese (Class II)	35 – 39.9
Obese (Class III)	40+

Worked examples

Metric example: A person weighing 70 kg with a height of 1.75 m → BMI = 70 ÷ (1.75 × 1.75) = 22.9 (Normal weight).
Imperial example: A person weighing 150 lbs at 5 ft 6 in (66 in) → BMI = 703 × 150 ÷ (66 × 66) = 24.2 (Normal weight).

Healthy weight range

A healthy BMI is between 18.5 and 24.9. For a person 175 cm tall, this corresponds to a weight range of 57.5 – 76.3 kg. Staying in this range reduces the risk of cardiovascular disease, diabetes, and obesity-related conditions.

Limitations of BMI

BMI does not measure body fat directly. It does not distinguish between fat and muscle mass, so athletes may show a high BMI but low body fat. Similarly, people with high body fat but low muscle mass may appear in the “normal” BMI category. Waist circumference and body fat calculators can provide additional insights.

BMI Calculator FAQs

1. What is BMI and why is it important?BMI, or Body Mass Index, is a measure of body weight relative to height. It is important because it helps identify whether a person is underweight, at a healthy weight, overweight, or obese, which can indicate risks for heart disease, diabetes, and other health conditions.

2. What is a healthy BMI range?The healthy BMI range for adults is 18.5 to 24.9. Staying within this range is associated with lower risks of cardiovascular disease, diabetes, and obesity-related illnesses.

3. Is BMI accurate for everyone?BMI is a useful screening tool, but it does not measure body fat directly. It may overestimate fat in athletes with high muscle mass and underestimate fat in older adults or those with low muscle mass.

4. Does BMI change with age?BMI is calculated the same way for all adults, but body composition changes with age. Older adults may have more body fat even at the same BMI compared to younger people. This is why combining BMI with waist circumference and body fat percentage gives a better picture of health.

5. What BMI is considered overweight or obese?A BMI of 25 to 29.9 is classified as overweight. A BMI of 30 or higher is considered obese. Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and Class III (40+).

6. Can BMI be different for men and women?The BMI formula is the same for men and women, but women naturally carry more body fat than men at the same BMI. This is why body fat percentage calculators can provide additional insights by gender.

7. What should I do if my BMI is outside the healthy range?If your BMI is outside the healthy range, consider lifestyle changes such as improved diet, regular physical activity, and reducing sedentary time. Always consult a healthcare professional for personalised advice.