BMI Calculator
Calculate your Body Mass Index (BMI) quickly to understand your current weight category and its possible health implications.
Understanding Your Body Mass Index (BMI)
Body Mass Index (BMI) is a calculation based on your height and weight. It is widely used as a screening method to identify weight ranges that may be associated with health risks. However, BMI does not measure body fat directly and cannot determine your overall health on its own.
| BMI Category | BMI Range |
|---|---|
| Underweight | Less than 18.5 |
| Normal Weight | 18.5–24.9 |
| Overweight | 25.0–29.9 |
| Obesity | 30.0 or greater |
What Your BMI Result Means
BMI is a screening number that compares your weight with your height. It can help identify weight ranges associated with possible health risks, but it is only one part of understanding your health.
- Below 18.5 (underweight): You may not be getting enough energy or nutrients. If you have lost weight without trying, speak with a healthcare professional.
- 18.5 to 24.9 (healthy range): This range is generally associated with lower weight-related health risk for many adults.
- 25 to 29.9 (overweight): Some health risks may increase, particularly when excess weight is carried around the waist.
- 30 or above (obesity): Weight-related health risks may be higher. Consider discussing your result with a healthcare professional.
How BMI Is Calculated
The standard metric formula is:
BMI = weight (kg) ÷ height (m)²
Example: A person weighing 70 kg with a height of 1.75 m has a BMI of:
70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9
For pounds and inches, the formula is:
BMI = 703 × weight (lb) ÷ height (in)²
For example, a person weighing 154 lb and measuring 69 inches tall has a BMI of approximately 22.7.
Age and sex do not change the adult BMI calculation itself. However, the standard adult BMI categories are intended for adults aged 20 and older. Children and teenagers need BMI assessments based on age and sex using growth charts. You can consult the NHS BMI calculator for further guidance.
Where BMI Falls Short
- Muscle counts as weight: Athletes and people with high muscle mass can have a high BMI despite having relatively low body fat.
- It ignores fat distribution: BMI cannot show whether fat is stored around the waist or elsewhere on the body.
- Older adults: Some older adults may have a BMI in the usual range but still have low muscle mass.
- Ethnic background matters: Some guidelines use different BMI action points for people from certain ethnic backgrounds, including South Asian populations. Ask a healthcare professional which guidance applies to you.
- Pregnancy: Standard BMI categories are not designed to assess weight status during pregnancy.
- Children and teenagers: They need age- and sex-specific BMI assessments rather than adult categories.
What to Do With Your Number
Treat BMI as a starting point, not a verdict. Consider other indicators of health, including waist measurement, energy levels, sleep, blood pressure and blood test results reviewed by a healthcare professional.
If you want to become more active, start with manageable steps and build a routine gradually. The World Health Organization recommends that adults aim for at least 150 minutes of moderate-intensity physical activity each week.
Explore our 5-minute morning micro workout or no-equipment home workout for simple ways to get moving. You can also try our calorie calculator for a general estimate of your daily calorie needs.
Frequently Asked Questions
Que.1 Is BMI accurate for everyone?Ans. No. BMI is a screening tool, not a diagnosis. It may be less informative for people with high muscle mass, older adults and some ethnic groups. A healthcare professional can consider additional measurements and individual circumstances.
Que.2 What is a healthy BMI?Ans. For most adults aged 20 and older, a BMI from 18.5 to 24.9 is generally classified as the healthy-weight range. Individual health needs vary, so discuss your result with a healthcare professional if you are unsure.
Que.3 Can I have a high BMI and still be healthy?Ans. Yes, this is possible, particularly for people with greater muscle mass. Health also depends on factors such as blood pressure, blood sugar, cholesterol, fitness and lifestyle habits.
Que.4 Does BMI work for children?Ans. Children and teenagers need BMI assessments that account for age and sex. Adult BMI categories should not be used to interpret their results.
Que.5 How often should I check my BMI?Ans. There is no single schedule for everyone. Checking occasionally or when your weight changes significantly may be sufficient for general awareness. Daily weight changes often reflect normal fluid fluctuations.
Que.6 What is the difference between BMI and body fat percentage?Ans. BMI uses height and weight to estimate a weight category. Body fat percentage estimates the proportion of your body weight that is fat. Each measurement has limitations, and neither provides a complete picture of health on its own.
Disclaimer
This calculator provides a general estimate and is not a medical diagnosis. If you have a medical condition, take medication, are pregnant, or are considering a major change to your diet or exercise routine, consult a qualified healthcare professional.