BMI Calculator — kg/cm or lb/ft-in
A BMI calculator with WHO categories and a healthy weight range
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BMI 23.5, Normal weight
BMI = 150 lb → 68.04 kg ÷ (1.7 m)² = 23.5
Healthy weight range: 118.1 lb to 159 lb (BMI 18.5 to 24.9)
Your weight is inside the healthy range.
Category cut-offs (BMI) · WHO adult categories
- UnderweightBelow 18.5
- Normal weight18.5 to 24.9
- Overweight (pre-obese)25 to 29.9
- Obesity class I30 to 34.9
- Obesity class II35 to 39.9
- Obesity class III40 or above
BMI is a rough screening number from height and weight only. It ignores muscle, body fat, age and sex, and it is not medical advice or a diagnosis. It may not suit children and teens, pregnant women or athletes, so talk to a health professional about your health.
What it is
BMI, or body mass index, is a quick screening number that relates weight to height. It appears in health checkups and weight discussions because it is simple to compute and compare. This calculator takes your height and weight in either metric or imperial units, returns the BMI with its WHO adult category, and goes a step further by showing the weight range that counts as normal for your height and how far you are from it.
How to use
- Choose your units: feet-inches with pounds, or centimeters with kilograms.
- Enter your height and weight. The BMI and category appear as you type.
- Check the table to see where you fall, and read the healthy range and the distance to it.
- Copy the result with the button beside the number.
How it works
- Formula: BMI = weight in kg ÷ (height in m)². The category uses the BMI rounded to one decimal place.
- WHO adult categories: under 18.5 underweight; 18.5 to 24.9 normal; 25 to 29.9 overweight (pre-obese); 30 to 34.9 obesity class I; 35 to 39.9 class II; 40 or above class III.
- Healthy range: the weights that give a BMI between 18.5 and 24.9 at your height.
- Unit conversion: exact definitions, 1 in = 2.54 cm and 1 lb = 0.45359237 kg.
- Input limits: heights from 50 to 272 cm and weights from 10 to 500 kg are accepted; anything outside is flagged as a probable typo.
- Not medical advice: this is a screening number, not a diagnosis. It is not suitable for children, teenagers, pregnant women or athletes with a lot of muscle.
Examples
| Height | Weight | BMI | WHO category |
|---|---|---|---|
| 5 ft 7 in | 150 lb | 23.5 | Normal weight |
| 5 ft 10 in | 200 lb | 28.7 | Overweight |
| 170 cm | 65 kg | 22.5 | Normal weight |
| 160 cm | 45 kg | 17.6 | Underweight |
At 170 cm the normal range is roughly 53.5 kg to 72.0 kg.
FAQ
How is BMI calculated?
Divide weight in kilograms by height in meters squared. A person 1.70 m tall weighing 65 kg has 65 ÷ (1.70 × 1.70) = 22.5. With pounds and inches the tool converts to metric first and shows the working.
What are the WHO categories?
For adults, below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 is overweight, and 30 or more is obesity, split into classes I (30 to 34.9), II (35 to 39.9) and III (40 or more).
Does a normal BMI mean I am healthy?
Not necessarily. BMI uses only height and weight, so it cannot see muscle, body fat, fat distribution, age or sex. Someone muscular can score high and someone with little muscle can score normal. Ask a clinician about your health.
Can children, pregnant women or athletes use it?
It is not designed for them. These categories are for adults. Children and teens are assessed on growth charts by age and sex, and pregnancy and heavy training change how weight should be read.
