BMI Calculator
BMI = weight in kg ÷ (height in m)^2, so 68 kg at 170 cm gives 68 ÷ 1.7^2 = 23.5, inside the healthy range of 18.5 to 24.9. The calculator takes metric or US units, shows the healthy weight range for your height and offers the lower cut-offs used for Asian and Indian adults.
By the Calculators With Steps team · Updated November 10, 2026 · How we check our math
- Healthy weight for your height
- 53.5 kg – 72 kg
- To reach a healthy BMI
- Already in range
- BMI Prime
- 0.94BMI ÷ 25; above 1.0 is over the healthy limit
- Ponderal index
- 13.8 kg/m³
Step-by-step working
- Height in metres: 1.7 m → squared: 2.89 m²
- Weight in kilograms: 68 kg
- BMI = 68 ÷ 2.89 = 23.53
BMI categories for adults (WHO)
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity (class I) |
| 35.0 – 39.9 | Obesity (class II) |
| 40 and above | Obesity (class III) |
BMI is a screening measure for adults aged 20 and over. It does not measure body fat directly and can misclassify very muscular people, older adults and pregnant women. For children and teens, use age- and sex-specific BMI percentiles.
How to use the BMI calculator
- Choose Metric to enter centimetres and kilograms, or US to enter feet, inches and pounds.
- Type your height and weight. The result updates as you type.
- Keep WHO / CDC cut-offs, or switch to Asian & Indian if you are of South Asian or East Asian descent.
You will see your BMI to one decimal place, your weight category, the weight range that counts as healthy for your height and how far you are from it.
BMI formula
Metric: BMI = weight (kg) ÷ height (m)²
US units: BMI = 703 × weight (lb) ÷ height (in)²
Example: someone 5 ft 9 in (69 inches) tall who weighs 150 lb has a BMI of 703 × 150 ÷ 69² = 105,450 ÷ 4,761 = 22.1, which is in the healthy range.
BMI chart for adults
| BMI | WHO / CDC category | Asian & Indian category |
|---|---|---|
| Below 18.5 | Underweight | Underweight |
| 18.5 – 22.9 | Healthy weight | Healthy weight |
| 23.0 – 24.9 | Healthy weight | Overweight |
| 25.0 – 29.9 | Overweight | Obesity |
| 30.0 and above | Obesity | Obesity |
Healthy weight range by height
Here is the weight range for a BMI of 18.5 to 24.9 at some common heights.
| Height | Healthy weight (kg) | Healthy weight (lb) |
|---|---|---|
| 152 cm (5 ft 0 in) | 42.7 – 57.5 | 94 – 127 |
| 160 cm (5 ft 3 in) | 47.4 – 63.7 | 104 – 140 |
| 168 cm (5 ft 6 in) | 52.2 – 70.3 | 115 – 155 |
| 175 cm (5 ft 9 in) | 56.7 – 76.3 | 125 – 168 |
| 183 cm (6 ft 0 in) | 62.0 – 83.4 | 137 – 184 |
What your BMI means
BMI is a quick, free way to screen for weight-related health risk across a population. Higher BMI is linked with greater risk of type 2 diabetes, high blood pressure, heart disease, sleep apnea and some cancers, and very low BMI is linked with nutritional deficiencies and bone loss. But BMI is only a starting point:
- It does not measure body fat or show where fat is stored. Fat around the waist carries more risk than fat on the hips.
- It treats muscle and fat alike, so strength athletes often read as “overweight”.
- It doesn’t account for age, sex or ethnicity, which is why separate Asian cut-offs exist.
For a fuller picture, pair BMI with your waist measurement. A waist over 102 cm (40 in) for men or 88 cm (35 in) for women indicates higher risk in most guidelines, and lower thresholds of 90 cm and 80 cm are often used for South Asians. You can also use the body fat calculator for a closer look at body composition.
BMI, waist-to-height ratio and body fat
Each of these measures answers a slightly different question:
- BMI compares weight with height. It is quick to calculate and useful for tracking change over time.
- Waist-to-height ratio divides waist circumference by height. Keeping it below 0.5 (your waist less than half your height) is a simple target that reflects belly fat, which BMI misses.
- Body fat percentage estimates how much of your weight is fat. It is the most direct measure of composition, but home methods such as tape measurements or smart scales have an error of several percentage points.
If two of the three point the same way, you can trust the signal more than any single number.
Next steps
If your BMI is outside the healthy range, small sustained changes work best. Use the calorie calculator or TDEE calculator to set a realistic daily intake, and aim for a loss of about 0.5 to 1 kg (1 to 2 lb) per week. Talk to your doctor before starting a weight-loss plan, especially if you have a medical condition, are pregnant or take medication.
BMI Calculator: frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. In US units it is 703 × weight in pounds ÷ height in inches squared. A person who is 170 cm tall and weighs 68 kg has a BMI of 68 ÷ 1.7² = 23.5.
What is a healthy BMI?
For most adults a BMI of 18.5 to 24.9 is classed as a healthy weight under WHO and CDC guidelines. Below 18.5 is underweight, 25 to 29.9 is overweight and 30 or more is obesity. For Asian and Indian adults many guidelines use 23 as the start of overweight and 25 as the start of obesity.
Is BMI different for men and women?
No. The adult BMI formula and categories are the same for men and women. Women tend to carry more body fat than men at the same BMI, which is one reason BMI is a screening tool rather than a diagnosis.
Why are BMI cut-offs lower for Asians and Indians?
Studies found that people of South Asian and East Asian descent have more body fat and a higher risk of type 2 diabetes and heart disease at a lower BMI than people of European descent. A WHO expert consultation in 2004 suggested 23 and 27.5 as public health action points, and Indian consensus guidelines use 23 for overweight and 25 for obesity.
Is BMI accurate for athletes and older adults?
Not always. BMI cannot tell muscle from fat, so muscular athletes can be labelled overweight, and older adults who have lost muscle can show a normal BMI despite high body fat. Waist circumference or a body fat estimate gives useful extra context.
Can I use this BMI calculator for children?
No. Children and teenagers aged 2 to 19 are assessed with BMI-for-age percentiles that account for age and sex, using CDC or WHO growth charts. This calculator uses adult cut-offs.
What BMI is considered obese?
A BMI of 30 or higher is classed as obesity for most adults, divided into class I (30 to 34.9), class II (35 to 39.9) and class III (40 or more). Under Asian and Indian cut-offs, obesity starts at a BMI of 25.
How we checked this page: every figure in the examples and FAQs above is produced by this calculator and verified by automated tests against known answers, and the rules and rates come from the sources below. Last updated . Spotted a problem? Tell us.