BMI Calculator
Work out your body mass index from your height and weight, see your category, and find the healthy weight range for your height.
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Body mass index, or BMI, is the most widely used quick check of whether a person’s weight is in a healthy range for their height. Doctors, insurers and public health researchers use it because it needs only two measurements and no special equipment. This calculator works in metric or US units, places your result in the standard adult categories, and shows the weight range that would count as healthy for your height.
How to use the BMI calculator
- Choose Metric (centimeters and kilograms) or US (feet, inches and pounds).
- Enter your height and weight. Measure in the morning without shoes for the most consistent reading.
- Your BMI, category and healthy weight range appear instantly.
The BMI formula
BMI = weight (kg) ÷ height (m)²
BMI = 703 × weight (lb) ÷ height (in)²Example: a person who is 175 cm (1.75 m) tall and weighs 72 kg has a BMI of 72 ÷ 1.75² = 72 ÷ 3.0625 ≈ 23.5, which is in the healthy range.
BMI categories for adults
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity, class 1 |
| 35.0 – 39.9 | Obesity, class 2 |
| 40.0 and above | Obesity, class 3 |
BMI Prime is your BMI divided by 25, the upper limit of the healthy range. A BMI Prime of 1.10 means you are 10% above that limit. A value below 0.74 means you are below 18.5.
What BMI can’t tell you
BMI is a useful screening number, but it has well-known limits:
- Muscle vs. fat. It can’t tell them apart, so muscular people may be labeled overweight.
- Fat distribution. Fat around the waist carries more health risk than fat on the hips and thighs, and BMI doesn’t see the difference. A waist measurement under half your height is a good companion check.
- Age and ethnicity. Older adults lose muscle, so the same BMI can hide more body fat. Risk thresholds also differ between ethnic groups.
- Pregnancy. BMI isn’t meaningful during pregnancy.
Use BMI as a starting point for a conversation with a healthcare professional, not as a verdict on your health.
Moving toward a healthy BMI
Small, sustainable changes beat crash diets. Aim for a modest calorie deficit or surplus, mostly whole foods, enough protein, regular strength and cardio exercise, and good sleep. A weight change of 0.25–0.5 kg (0.5–1 lb) per week is a realistic, healthy pace for most adults.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI from 18.5 to 24.9 is considered a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above falls into the obesity categories.
Is BMI accurate for athletes and muscular people?
Not very. BMI can't tell muscle from fat, so strong, muscular people often score as "overweight" while being very lean. Waist measurement or a body fat estimate gives a better picture for them.
Is the BMI calculation different for men and women?
No. Adults of every sex use the same formula and categories. Women naturally carry more body fat than men at the same BMI, which is one reason BMI is best used as a screening tool rather than a diagnosis.
Can children use this BMI calculator?
No. For people under 20, BMI is interpreted with age- and sex-specific growth percentiles. A doctor or a pediatric BMI-for-age chart should be used instead.
Do some groups use different BMI cut-offs?
Yes. Health risks rise at lower BMIs for people of Asian descent, so some health authorities recommend 23 as the threshold for overweight and 27.5 for obesity in these populations.