BMI Calculator
Body mass index (BMI) compares your weight with your height. Enter both in metric or imperial units to see your BMI, the category it falls into and the weight range that corresponds to a healthy BMI at your height.
Results
Your BMI
23.5 kg/m²
- Category
- Normal weight
- Healthy weight for your height
- 53.5 – 72 kg
- BMI 18.5 to 24.9
A height of 170 cm and weight of 68 kg gives a BMI of 23.5, which is in the "Normal weight" range.
Where your BMI sits
- Underweight: below 18.5
- Normal weight: 18.5 to 25
- Overweight: 25 to 30
- Obesity: 30 and above
Show the calculation steps
- Convert the height to metres: 170 cm = 1.7 m.
- BMI = weight (kg) ÷ height (m)² = 68 ÷ 2.89 = 23.5.
- A BMI of 23.5 falls in the "Normal weight" range.
- A BMI between 18.5 and 24.9 at your height corresponds to 53.5 – 72 kg.
- BMI is a screening measure. It does not distinguish muscle from fat and is not designed for children, teenagers or pregnant women.
What BMI tells you
BMI is a quick screening number used by health services worldwide. It does not measure body fat directly, but for most adults it is a reasonable indicator of whether weight may be affecting health risks.
The categories used here follow the World Health Organization's adult classification: under 18.5 is underweight, 18.5 to 24.9 is a healthy range, 25 to 29.9 is overweight, and 30 or above is obesity, split into three classes.
How your category is decided
The calculator rounds your BMI to one decimal place and then compares it with the boundaries above, so the category always matches the number you see. The healthy weight range is the weight at your height that gives a BMI of 18.5 and 24.9.
Limits of BMI
BMI cannot tell muscle from fat, so athletes and very muscular people can have a high BMI without excess body fat. It also does not account for age, sex, ethnicity or where fat is carried, and different thresholds are sometimes used for some populations.
This calculator is meant for adults. For children and teenagers, BMI is compared with age- and sex-specific growth charts, which this tool does not use.
Formula
BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lb) ÷ height (in)²
Where:
- weight
- = Body weight in kilograms (or pounds)
- height
- = Height in metres (or inches)
Example calculation
170 cm and 68 kg
Inputs
- Units
- Metric (cm, kg)
- Height
- 170 cm
- Weight
- 68 kg
Result
- Your BMI
- 23.5 kg/m²
- Category
- Normal weight
- Healthy weight for your height
- 53.5 – 72 kg
Step-by-step
- Convert the height to metres: 170 cm = 1.7 m.
- BMI = weight (kg) ÷ height (m)² = 68 ÷ 2.89 = 23.5.
- A BMI of 23.5 falls in the "Normal weight" range.
- A BMI between 18.5 and 24.9 at your height corresponds to 53.5 – 72 kg.
5 ft 7 in and 150 lb
Inputs
- Units
- Imperial (ft, in, lb)
- Height (feet)
- 5 ft
- Height (inches)
- 7 in
- Weight
- 150 lb
Result
- Your BMI
- 23.5 kg/m²
- Category
- Normal weight
- Healthy weight for your height
- 118.1 – 159 lb
Step-by-step
- Convert to metric: 5 ft 7 in = 1.702 m and 150 lb = 68.04 kg.
- BMI = weight (kg) ÷ height (m)² = 68.04 ÷ 2.8961 = 23.5.
- A BMI of 23.5 falls in the "Normal weight" range.
- A BMI between 18.5 and 24.9 at your height corresponds to 118.1 – 159 lb.
Important notes
- BMI is a screening tool, not a diagnosis. Talk to a healthcare professional before making decisions about your health.
- Not suitable for children, teenagers, pregnant women or people with a high proportion of muscle mass.
Disclaimer: This calculator provides general estimates for informational purposes and is not medical advice. Results do not account for individual factors such as age, muscle mass, medical conditions or ethnicity. Speak to a qualified healthcare professional about your health.
Frequently asked questions
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. Someone who is 1.70 m tall and weighs 68 kg has a BMI of 68 ÷ 1.70² = 23.5. In imperial units the same result comes from 703 × weight in pounds ÷ height in inches squared.
What is a healthy BMI?
For most adults, a BMI from 18.5 to 24.9 is considered the healthy range. Values below 18.5 are classed as underweight, 25 to 29.9 as overweight and 30 or more as obese.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so people with a lot of muscle can have a high BMI while having low body fat. Waist measurement or body fat percentage can give a fuller picture.
Does BMI depend on age or sex?
The adult formula and categories are the same for men and women, but they are not appropriate for children and teenagers. Older adults and some ethnic groups may have different healthy ranges, so ask a professional for personal advice.
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