BMI Calculator: Check Your Body Mass Index (Adults)
Use this free BMI calculator to check your Body Mass Index in seconds. Enter your height and weight to see your BMI, your weight category, the healthy weight range for your height, and how much you would need to gain or lose to reach it. Choose between the standard World Health Organization (WHO) categories and the Asian-population categories. Works in imperial (lbs, ft) and metric (kg, cm). For adults aged 18 and over.
Scale: BMI 15 to 40.
Your numbers
BMI categories
BMI is a screening tool, not a diagnosis. It does not measure body fat directly or distinguish muscle from fat.
What Is BMI (Body Mass Index)?
Body Mass Index (BMI) is a number calculated from your weight and height that is used to screen for weight categories that may lead to health problems. It was developed in the 1830s by the Belgian mathematician Adolphe Quetelet and is now used worldwide by doctors, researchers and health organizations because it is quick, free and easy to calculate.
How to Calculate BMI
Imperial: BMI = 703 x weight (lbs) / height (in)^2
For example, a person who weighs 70 kg and is 1.75 m tall has a BMI of 70 / (1.75 x 1.75) = 22.9. A person who weighs 160 lbs and is 5 ft 8 in (68 in) has a BMI of 703 x 160 / (68 x 68) = 24.3.
BMI Categories for Adults (WHO)
| BMI | Category |
|---|---|
| Below 16 | Severe thinness |
| 16 - 16.9 | Moderate thinness |
| 17 - 18.4 | Mild thinness |
| 18.5 - 24.9 | Normal (healthy) weight |
| 25 - 29.9 | Overweight |
| 30 - 34.9 | Obese (Class I) |
| 35 - 39.9 | Obese (Class II) |
| 40 and above | Obese (Class III) |
BMI Categories for Asian Adults
Research shows that many Asian populations develop health problems such as type 2 diabetes and heart disease at a lower BMI than other groups. Because of this, WHO Asia-Pacific guidelines use lower cut-offs:
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 - 22.9 | Normal weight |
| 23 - 24.9 | Overweight (at risk) |
| 25 - 29.9 | Obese (Class I) |
| 30 and above | Obese (Class II) |
Use the option above the button to switch between the two.
What Is a Healthy BMI?
For most adults, a healthy BMI is between 18.5 and 24.9 (18.5 to 22.9 using the Asian cut-offs). Both being below and above this range are linked with higher health risks. Being underweight is associated with nutrient deficiencies, weakened immunity and bone loss. Being overweight or obese is linked with a higher risk of type 2 diabetes, high blood pressure, heart disease, sleep apnea and some cancers.
Limitations of BMI
BMI is useful for large groups, but for an individual it can be misleading. Keep these limits in mind:
- It does not measure body fat. A muscular athlete can have a high BMI and very low body fat.
- It ignores fat distribution. Fat stored around the waist (belly fat) is riskier than fat stored on the hips and thighs.
- It can underestimate risk in some people. Someone with a "normal" BMI but low muscle and high body fat is sometimes called "normal weight obese".
- It varies by age. Older adults may have more body fat at the same BMI, while a slightly higher BMI can be protective in later life.
- It varies by ethnicity. Health risks can differ at the same BMI between ethnic groups.
- It is not for children and teens. For ages 2 to 19, BMI is compared with age- and sex-specific percentiles on growth charts.
- It is not suitable during pregnancy. Weight gain is expected and healthy.
Better Measures to Use With BMI
- Waist circumference: a waist above about 102 cm (40 in) for men or 88 cm (35 in) for women is linked with higher health risk. Asian guidelines use lower cut-offs of about 90 cm for men and 80 cm for women.
- Waist-to-height ratio: keeping your waist below half your height is a simple, useful guide.
- Body fat percentage: shows what your weight is made of. Try the Body Fat Calculator.
- Blood tests and blood pressure: your doctor can check markers such as blood sugar, cholesterol and blood pressure, which matter more than any single number.
How to Move Toward a Healthy BMI
If you need to lose weight
- Create a moderate calorie deficit of about 10-20% below maintenance. Use the Calorie Deficit Calculator to find your number.
- Aim to lose about 0.5-1% of your body weight per week.
- Eat plenty of protein and vegetables, and lift weights to protect muscle.
- Walk daily and sleep 7-9 hours.
If you need to gain weight
- Eat slightly above your maintenance calories, about 250-500 extra per day.
- Include strength training so the extra weight is mostly muscle.
- Choose calorie-dense, nutritious foods such as nuts, whole grains, dairy, eggs and healthy oils.
- Speak to a doctor if you are underweight without trying, as there can be a medical cause.
Frequently Asked Questions About BMI
What is a healthy BMI?
For most adults, a healthy BMI is between 18.5 and 24.9. For many Asian populations, guidelines suggest a healthy range of 18.5 to 22.9.
How do I calculate my BMI?
Divide your weight in kilograms by your height in meters squared. In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared. Or just use the calculator above.
Is BMI accurate?
BMI is a reasonable screening tool for most people, but it does not measure body fat or fat distribution. It can overestimate risk in muscular people and underestimate it in people with low muscle mass. Use it together with waist size and body fat percentage.
Is a BMI of 25 bad?
A BMI of 25 is just at the start of the overweight range. It does not automatically mean poor health. Look at your waist size, fitness, blood pressure and blood tests for a fuller picture.
Is BMI different for men and women?
The BMI formula and adult categories are the same for men and women. However, at the same BMI, women generally have a higher body fat percentage than men.
Does BMI work for athletes and bodybuilders?
Not very well. Muscle weighs more than fat, so muscular people can be classified as overweight or obese even with low body fat. Body fat percentage is a better measure for them.
What is a healthy BMI for older adults?
Some research suggests a BMI slightly above 25, up to about 27 to 30, may be associated with better outcomes in people over 65 because it can protect against frailty. Ask your doctor what is right for you.
Disclaimer: This calculator is for educational purposes only and is not medical advice. BMI is a screening tool and does not diagnose health conditions. Consult a doctor or registered dietitian for personal advice, especially if you are pregnant, have a medical condition, or have a history of disordered eating.
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