BMI Calculator (Body Mass Index)

What is BMI?

Body Mass Index (BMI) is a number calculated from your height and weight. Doctors and health organisations such as the World Health Organization (WHO) use it as a quick screening tool to check whether a person's weight falls in a typical range for their height. BMI is free, fast and needs no equipment, which is why it is one of the most widely used health measurements in the world.

BMI does not measure body fat directly. It gives a general picture, so it works best as a starting point rather than a final answer about your health.

How to use this BMI calculator

Choose Metric if you know your height in centimetres and weight in kilograms, or Imperial if you use feet, inches and pounds. Enter your height and weight, add your age and sex, and press Calculate BMI. You will instantly see your BMI score, your weight category, where you sit on the colour scale, and a list of everyday foods that suit your result.

BMI formula

The calculator uses the standard BMI formula:

Metric: BMI = weight (kg) ÷ [height (m)]²

Imperial: BMI = 703 × weight (lb) ÷ [height (in)]²

Example: A person who is 170 cm tall and weighs 65 kg has a BMI of 65 ÷ (1.70 × 1.70) = 22.5, which falls in the healthy weight range. In imperial units, someone who is 5 ft 7 in (67 inches) and weighs 145 lb has a BMI of 703 × 145 ÷ (67 × 67) = 22.7.

BMI chart for adults

For adults aged 20 and over, the WHO uses these standard BMI categories for both men and women:

BMI range	Category
Below 18.5	Underweight
18.5 – 24.9	Healthy weight
25.0 – 29.9	Overweight
30.0 and above	Obese

Healthy weight range by height

This table shows the weight range that gives a healthy BMI (18.5 to 24.9) at common heights. Use it to see a realistic target for your own height.

Height	Healthy weight range
150 cm (4 ft 11 in)	41.6 – 56.0 kg
155 cm (5 ft 1 in)	44.4 – 59.8 kg
160 cm (5 ft 3 in)	47.4 – 63.7 kg
165 cm (5 ft 5 in)	50.4 – 67.8 kg
170 cm (5 ft 7 in)	53.5 – 72.0 kg
175 cm (5 ft 9 in)	56.7 – 76.3 kg
180 cm (5 ft 11 in)	59.9 – 80.7 kg
185 cm (6 ft 1 in)	63.3 – 85.2 kg
190 cm (6 ft 3 in)	66.8 – 89.9 kg

For a more personal target based on your frame and sex, try our Ideal Weight Calculator.

BMI for South Asian and Asian adults

Research has shown that people of South Asian and East Asian background, including people from Pakistan and India, tend to face higher health risks such as type 2 diabetes and heart disease at a lower BMI than other groups. For this reason, a WHO expert panel suggested lower action points for Asian populations: a BMI of 23 or more may already signal increased risk, and 27.5 or more signals high risk. If you are of Asian background and your BMI is between 23 and 25, it is worth paying extra attention to diet, activity and waist size.

BMI for children and teens

The adult categories above do not apply to children and teenagers. For ages 2 to 19, BMI is compared against growth charts for the same age and sex and reported as a percentile. For example, a BMI at or above the 95th percentile is classed as obese, while one below the 5th percentile is classed as underweight. If you are checking BMI for a child, use the result only as a rough guide and speak with a paediatrician for a proper assessment.

Limitations of BMI

BMI doesn't distinguish between muscle and fat, so athletes and very muscular people may show a high BMI without carrying excess body fat. It also doesn't show where fat is stored. Fat around the waist is linked with higher health risk than fat elsewhere. BMI may also be less accurate for older adults, who often lose muscle with age, and it is not suitable during pregnancy. For a fuller picture, pair your result with our Body Fat Calculator and Lean Body Mass Calculator.

How to improve your BMI

If your BMI is above the healthy range, small and steady changes work better than crash diets. Aim for regular meals with plenty of vegetables, daal and lean protein, cut back on sugary drinks and fried snacks, and add at least 30 minutes of walking or other activity on most days. If your BMI is below the healthy range, focus on nutrient-rich, calorie-dense foods such as milk, eggs, nuts and whole grains. Our Calorie Calculator and Macro Calculator can help you set daily targets, and the Water Intake Calculator shows how much water you need.

Frequently Asked Questions

What is a healthy BMI range?

For most adults, a BMI between 18.5 and 24.9 is considered healthy. For adults of South Asian or Asian background, staying below 23 is often recommended because health risks can start at a lower BMI.

Is the BMI calculator different for men and women?

No. The BMI formula and adult categories are the same for men and women. However, women naturally carry more body fat than men at the same BMI, which is why a body fat test can give extra detail.

Is BMI accurate for everyone?

BMI is a useful screening tool but not a perfect one. It can overestimate body fat in muscular people and athletes, and underestimate it in older adults who have lost muscle.

How do I calculate BMI in kg and feet?

Convert your height to metres first (1 foot = 0.3048 m, 1 inch = 0.0254 m), then divide your weight in kg by your height in metres squared. Or simply choose the Imperial option above and the calculator will convert everything for you.

What BMI is considered obese?

For adults, a BMI of 30 or higher is classed as obese. A BMI of 40 or higher is often called severe obesity, and speaking with a doctor is strongly recommended at that level.

How often should I check my BMI?

Checking every one to three months is enough for most people to track weight trends. Weigh yourself at the same time of day, ideally in the morning, for consistent results.