BMI Calculator
Calculate your Body Mass Index and find out if you're in a healthy weight range.
Measure around your belly button — unlocks waist-to-height ratio
Your Result
Your BMI
24.5
Normal weight
Healthy Weight (min)
56.7 kg
BMI 18.5
Healthy Weight (max)
76.6 kg
BMI 25.0
24.5
Normal
Great work! Maintain your healthy weight with balanced nutrition and regular exercise.
Your weight vs. healthy range
✓ Your weight is within the healthy range.
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | → Normal weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obese |
BMI is a screening tool, not a diagnosis. It doesn't distinguish muscle from fat or account for age, sex, ethnicity, or body composition. Athletes may read as "Overweight" despite low body fat, and older adults may read "Normal" with low muscle mass. For children and teens, age- and sex-specific percentile charts should be used instead. Treat this as a starting point, not a verdict — consult a healthcare professional for a full assessment.
How to use this calculator
- Choose metric or imperial units.
- Enter your weight and height using the sliders or number fields.
- (Optional) Enter your waist measurement to also see your waist-to-height ratio — a useful second indicator.
The gauge shows your BMI and category, with the healthy weight range for your height and how far your weight sits from it.
How it works
Body Mass Index is a simple ratio of weight to height:
BMI = weight (kg) ÷ height (m)²
It places that single number into one of four WHO categories — underweight, normal, overweight, obese — the same thresholds for everyone.
What BMI cannot do is just as important. It does not know whether your weight is muscle or fat, and it does not adjust for age, sex or body type. That is why a fit, muscular person may score as “overweight” and why BMI is best read as a quick screening signal — not a verdict on health.
The optional waist-to-height ratio addresses one of BMI’s blind spots: it reflects where fat is stored. A waist under half your height is the simple guideline. Used together, the two numbers give a fuller picture than either alone.
Frequently Asked Questions
How is BMI calculated? ▾
BMI is your weight in kilograms divided by the square of your height in metres (kg/m²). In imperial units it is weight in pounds divided by height in inches squared, multiplied by 703. It is a single number that relates weight to height — nothing more.
What are the BMI categories? ▾
The World Health Organization classifies adult BMI as: under 18.5 underweight, 18.5 to 24.9 normal weight, 25.0 to 29.9 overweight, and 30.0 or above obese. These thresholds are the same for men and women and apply only to adults.
Is BMI an accurate measure of health? ▾
BMI is a screening tool, not a diagnosis. It does not distinguish muscle from fat, or account for age, sex, ethnicity or body composition. A muscular athlete can register as overweight; an older person with low muscle mass can register as normal while carrying excess fat. Treat it as a starting point, alongside other measures and a doctor's assessment.
Why is waist-to-height ratio also useful? ▾
BMI ignores where fat is carried. Waist-to-height ratio — keeping your waist under half your height — reflects central fat, which is more closely tied to health risk. It works across body types where BMI can mislead, which is why this calculator offers it as an optional second measure.
Does BMI work for children? ▾
No. The adult categories do not apply to children and teenagers, whose body composition changes with growth. Under-20s should be assessed with age- and sex-specific BMI percentile charts instead.