Enter your height and weight to instantly calculate your Body Mass Index, find your healthy weight range, and understand your BMI category. Supports metric and imperial units — free, no signup required.
Body Mass Index (BMI) is a value derived from height and weight. Enter your details to visualize your results.
* These ranges apply to adults aged 18 and above. BMI interpretation differs for children and teens.
BMI, or Body Mass Index, is a numerical value calculated from your height and weight that estimates whether your body weight falls within a healthy range for your height. Healthcare providers, nutritionists, and public health organisations worldwide use it as a standard first-step screening tool to assess weight-related health risk — not because it tells the complete picture, but because it requires no specialist equipment, costs nothing, and produces an instant result.
The concept was originally developed by Belgian mathematician Adolphe Quetelet in the 1830s and was later adopted by the World Health Organization as a global standard for classifying adult weight status. Today it remains one of the most widely referenced health metrics in clinical practice, public health research, and everyday personal health tracking.
Body Mass Index is calculated the same way for both men and women. The result is compared against standard weight categories to determine whether a person is underweight, in the normal weight range, overweight, or obese.
This BMI calculator uses the standard formulas recognised by the WHO and medical community worldwide.
Metric formula
BMI = Weight (kg) ÷ Height (m²)
Imperial / US formula
BMI = (Weight (lbs) ÷ Height (in²)) × 703
Both formulas produce the same result — the choice between them depends on which unit system you prefer. Enter your height and weight, choose metric (cm/kg) or imperial (inches/lbs), and your BMI value and category are displayed immediately. You do not need to create an account, download anything, or share personal data. Everything runs directly in your browser.
Once you receive your BMI number, here is how to interpret it using the standard WHO adult classification for people aged 20 and older:
A BMI under 18.5 suggests body weight may be too low relative to height. This can sometimes be associated with nutritional deficiencies, a weakened immune system, or reduced bone density. If you consistently fall in this range, a conversation with a healthcare provider is worthwhile.
This is the healthy weight range associated with the lowest risk of weight-related health conditions for most adults. People in this category face a statistically lower risk of type 2 diabetes, hypertension, and cardiovascular disease compared to those in other categories.
A BMI in this range suggests carrying more body weight than is considered optimal for your height. Lifestyle changes including a more balanced diet and increased physical activity can often bring BMI back into the normal weight range over time.
A BMI of 30 or higher is classified as obese, further divided into Class I (30–34.9), Class II (35–39.9), and Class III (40 and above). Higher values in this range are associated with increased risk of serious conditions including heart disease, stroke, sleep apnea, type 2 diabetes, and certain cancers.
A BMI between 18.5 and 24.9 maps to a different body weight depending on how tall you are. For an adult standing 5 feet 7 inches (170 cm), the weight that falls within a normal BMI sits roughly between 118 and 159 pounds (54 to 72 kg). For someone at 5 feet 10 inches (178 cm), that same BMI range corresponds to approximately 129 to 174 pounds (59 to 79 kg).
These figures are useful reference points, but they are not a precise target. BMI is a screening measure that does not account for individual differences in muscle mass, bone density, or body composition. Use this range as a starting guide, not a strict personal goal.
The BMI formula is identical for men and women, but body composition naturally differs between them. Women typically carry a higher proportion of body fat than men at the same BMI value — meaning a woman and a man with the same number may have quite different body fat percentages. This does not change the standard BMI categories, but it is useful context when interpreting your result.
For older adults, additional consideration applies. Muscle mass tends to decrease and body fat tends to increase as people age, even when total body weight stays stable. An older adult with a BMI in the normal range may still carry a higher proportion of body fat than a younger person at the same reading. Some research suggests adults over 65 may benefit from sitting slightly higher in the BMI range compared to younger adults — though this should always be discussed with a doctor rather than used as a self-guided target.
BMI is a useful screening tool, but it is not a perfect measure of health or body composition. Here are the key things it does not account for:
Muscle mass vs. fat mass
BMI only looks at total weight in relation to height. A professional athlete with dense muscle may have a high BMI but very low body fat. Conversely, someone with a normal BMI may carry a high proportion of body fat with little muscle — sometimes called normal weight obesity.
Fat distribution and visceral fat
Where fat is stored matters as much as how much is present. Visceral fat stored around the abdominal organs carries significantly higher health risks than fat stored in the hips and thighs. BMI cannot measure fat distribution or identify where excess weight is being carried.
Age and sex differences
As people age, body composition naturally shifts toward less muscle and more fat even at the same body weight. Women also tend to carry more body fat than men at the same BMI. These variations are not captured in the standard BMI classification.
Ethnicity
Research shows that weight-related health risks can appear at lower BMI values in certain ethnic groups, particularly those of South Asian descent. Several health authorities publish adjusted BMI thresholds for these populations, recognising that standard cut-off points may not accurately reflect risk for all groups.
Children and teenagers
Standard adult BMI ranges do not apply to those under 18. For young people, BMI must be assessed against age- and sex-specific growth charts. The raw number alone carries no meaning without that age-adjusted context.
Use this calculator as a starting point, not a final verdict. For a thorough understanding of your health, combine BMI with other assessments such as waist circumference, body fat percentage, blood pressure, cholesterol levels, and a conversation with your doctor.
BMI is the most widely used screening metric because it needs only two inputs and no specialist equipment. However, other tools can provide information that BMI alone cannot capture.
Waist circumference
A direct measure of abdominal fat. A waist measurement above 88 cm (35 inches) for women or 102 cm (40 inches) for men is generally considered a risk indicator for metabolic conditions, regardless of BMI category.
Body fat percentage
Measures what proportion of total body weight comes from fat tissue. More informative than BMI for people with high muscle mass such as athletes, or those who have lost muscle with age.
Waist-to-hip ratio
Compares waist and hip measurements to assess how fat is distributed across the body. A higher ratio indicates more abdominal fat, which carries greater cardiovascular and metabolic risk than fat stored elsewhere.
Getting your BMI into a healthy range — and keeping it there — is less about willpower and more about building habits that feel sustainable month after month. No crash diets, no six-days-a-week gym schedules. Just practical shifts that compound quietly over time.
Build your meals around real ingredients
Heavily processed foods are engineered to make you eat past your hunger. When most of what you eat comes from whole sources — vegetables, pulses, eggs, fish, nuts, whole grains — your body regulates appetite far more reliably.
Shrink the package, not the pleasure
Calorie counting is exhausting. A simpler approach is to serve slightly less than you think you want, eat slowly, and check in halfway through. Your brain needs about 20 minutes to register fullness.
Move in ways you will actually repeat
The most effective exercise for weight management is whatever you will still be doing six months from now. A daily 30-minute walk beats an intense gym routine abandoned in three weeks. Adults generally benefit from building consistent moderate movement into their weekly routine.
Treat sleep as a health tool
When you regularly get under six hours, hunger hormones spike and fullness hormones drop. The result is stronger cravings and harder fat loss — even if your diet and exercise are solid. Target 7–9 hours nightly.
Deal with stress before it deals with your waistline
Sustained high stress keeps cortisol elevated, which encourages fat storage around the midsection. Even ten minutes of walking outside, breathwork, or journaling can meaningfully lower your baseline stress over time.
Replace liquid calories first
Sugary drinks, flavoured coffees, juices, and alcohol pack significant calories that do almost nothing to reduce hunger. Swapping these for water, plain tea, or black coffee is one of the highest-return changes you can make.
This tool is built for any adult who wants a clear, honest number — calculated quickly, privately, and without signing up for anything.
It is particularly useful if you are starting a health or fitness goal and want an objective baseline before you begin. Having a concrete starting point makes progress measurable and keeps motivation grounded in data rather than feelings.
It is equally valuable for people who are already on a health journey and want to check in periodically. BMI alone will not tell you everything, but tracking it alongside how you feel, your energy levels, and your fitness performance gives a fuller picture of how your body is changing over time.
Some people use it simply before a routine health check-up — to arrive already knowing their number and have a more informed conversation with their doctor or nurse.
One clear boundary: this BMI calculator is designed for adults aged 18 and above. BMI thresholds work differently for children and adolescents, whose healthy ranges shift with age and development stage and require age-adjusted growth charts to interpret correctly.
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A BMI Calculator is a tool that estimates your Body Mass Index based on your height and weight to assess whether you are underweight, normal, overweight, or obese.
BMI is calculated using the formula: BMI = weight (kg) ÷ [height (m)]². The BMI Calculator does this automatically for you.
BMI provides a general estimate of body fat, but it may not fully account for muscle mass, body composition, or age. It is a useful guideline, not a medical diagnosis.
Enter your weight and height into the calculator, select your gender if needed, and it will display your BMI along with the weight category.
A healthy BMI for most adults ranges from 18.5 to 24.9. This range indicates normal weight relative to height.
Yes, BMI can change as you age due to changes in muscle mass and body composition, but the standard BMI ranges are generally used for adults.
For adult females, a normal BMI typically ranges from 18.5 to 24.9, similar to males, though body composition may vary.
BMI is calculated by dividing a person’s weight in kilograms by the square of their height in meters: BMI = weight ÷ height².
Your BMI depends on your height. For example, a person weighing 70 kg and 1.75 m tall has a BMI of 22.9, which is considered normal.
BMI for age is used for children and teens to assess growth patterns. Adults generally use standard BMI ranges regardless of age.
* While this tool can point you in a useful direction, it is not a clinical assessment. If your result concerns you, or if you have an existing health condition, the right next step is a conversation with a qualified medical professional.