BMI Calculator

BMI Calculator

BMI Calculator

Free online BMI calculator to help you calculate your body mass index and understand your health status

BMI Classification

BMI RangeClassificationHealth RiskSuggestion
< 18.5UnderweightMalnutrition, low immunityIncrease high-calorie food intake
18.5 - 24.9NormalLow health riskBalanced diet
25 - 29.9OverweightIncreased cardiovascular riskReduce high-calorie food intake
≥ 30ObeseMultiple chronic disease risksStrict diet control

BMI Standards by Region

RegionUnderweightNormalOverweightObese
China< 18.518.5 - 23.924.0 - 27.9≥ 28.0
WHO / World Health Organization< 18.518.5 - 24.925.0 - 29.9≥ 30.0
Japan< 18.518.5 - 24.9No such band≥ 25.0
Singapore< 18.518.5 - 22.923.0 - 27.4≥ 27.5
Korea< 18.518.5 - 22.923.0 - 24.9≥ 25.0

Note: BMI classification standards vary slightly across countries and regions, mainly due to racial differences and regional population characteristics.

See the full cut-point table with sources for WHO, WS/T 428, Hong Kong DH, HPB, JASSO, KSSO and ADA 2026 →

BMI Calculation Formula and Standards

BMI = Weight(kg) / Height(m)²

Dietary and Exercise Recommendations

Underweight

Underweight (BMI < 18.5): Eat more quality protein foods such as fish and dairy, increase staple food intake such as rice and bread, and include more vegetables and nuts. Combine this with strength training to build muscle and gradually increase total calorie intake.

Normal

Normal (BMI 18.5 - 23.9): Mix coarse and fine grains in a ratio of about 1:6, replace some white flour with whole wheat flour, and keep staple food to one small bowl per meal. Eat more vegetables and fruit, prefer unsweetened fruit, choose fish, shrimp and chicken more often, limit pork, beef and lamb, control fat intake, and use light seasoning such as vinegar and soy sauce.

Overweight

Overweight (BMI 24 - 29.9): Control total calories, appropriate dietary records to maintain daily calorie intake, increase dietary fiber, vegetables and fruits, reduce high-sugar and high-fat foods, eat less refined carbohydrates such as white rice, white flour, eat more miscellaneous grains and coarse grains.

Obese

Obese (BMI ≥ 30): Strictly control calories, limit staple foods to reduce carbohydrate intake, avoid high-calorie foods, snacks and desserts, watch for hidden sugars and fats, and build a practical meal plan with moderate portions.

Recommended Exercise

  • Underweight (BMI < 18.5): Strength training, high-intensity interval training, swimming.
  • Normal (BMI 18.5 - 23.9): Aerobic exercise, strength training, yoga and other maintenance exercises.
  • Overweight (BMI 24 - 29.9): Aerobic exercise, strength training, high-intensity interval training.
  • Obese (BMI ≥ 30): Low-impact aerobic exercise, strength training, walking.

What is BMI?

BMI stands for Body Mass Index, also known as the Quetelet index. It is an internationally recognized standard for measuring body weight relative to height, commonly used to assess whether a person is underweight, normal weight, overweight, or obese.

In simple terms, BMI is calculated by dividing your weight in kilograms by your height in meters squared. It serves as a screening tool to assess weight-related health risks.

This free online BMI calculator provides instant BMI calculation — simply enter your height and weight to get your BMI value immediately.

How to Calculate BMI?

How to calculate BMI? The BMI formula is straightforward. You just need your height and weight:

BMI Formula: BMI = Weight(kg) ÷ Height(m)²

Example (Height: 170cm, Weight: 65kg):

  1. Convert height to meters: 170cm = 1.70m
  2. Square the height: 1.70 × 1.70 = 2.89
  3. Divide weight by height squared: 65 ÷ 2.89 ≈ 22.5
  4. BMI result: 22.5, within normal range

Using our free online BMI calculator, simply enter your height and weight and the system will automatically calculate your BMI and assess your health status.

What is the Normal BMI Range?

According to Chinese standards, the normal BMI range for adults is 18.5-23.9. A BMI value within this range is considered a healthy weight.

BMI < 18.5 (Underweight)

Underweight, may indicate malnutrition risk.

BMI 18.5-23.9 (Normal)

Healthy weight, low health risk.

BMI 24.0-27.9 (Overweight)

Above normal weight, increased cardiovascular risk.

BMI ≥ 28.0 (Obese)

Obese, significantly increased risk of chronic diseases.

Note: The above are Chinese BMI standards. Different countries have slightly different BMI ranges. It is recommended to combine body fat percentage and waist circumference for a comprehensive health assessment.

BMI Formula & Calculation Method

Standard BMI Formula

BMI = Weight(kg) ÷ Height²(m²)

This is the most universally used BMI formula, applicable to adults aged 18 and above. It was originally proposed by Belgian mathematician Adolphe Quetelet in the 19th century.

Imperial BMI Formula

BMI = Weight(lb) ÷ Height²(in²) × 703

If you use pounds and inches, use this formula. The 703 factor converts imperial units to metric.

Our online BMI calculator automatically handles all unit conversions.

What is the healthy BMI range?

China BMI index healthy standard range for men and women: 18.5~23.9.

WHO international (World Health Organization) BMI index standard healthy range for men and women: 18.5 ~ 24.9.

Japan BMI index healthy standard range for men and women: 18.5 ~ 22.9.

Singapore BMI index healthy standard range for men and women: 18.5 ~ 22.9.

Are BMI standards the same for men and women?

World Health Organization (WHO) standards and various national BMI standards do not differentiate between men and women.

The normal BMI range is 18.5-23.9.

The most beautiful body shape for women has a BMI value of 19,

The most beautiful body shape for men has a BMI value of 22.

Is BMI the same as body fat percentage?

BMI is not body fat percentage,

Online Body Fat Percentage Calculator (BFR)

BMI cannot reflect body fat content,

And excessive fat content is the factor that harms health.

People for whom BMI is not suitable

  1. Under 18 years old;
  2. Pregnant or breastfeeding;
  3. Physically weak or sedentary elderly.

Measurement Guide & Tips

Height Measurement

Correct height measurement is important for calculating BMI and body fat percentage.

  • Stand straight with heels, buttocks, and shoulders against the wall
  • Measure without shoes, looking straight ahead
  • Use a height meter or mark on the wall and measure with a tape
  • Morning height is 1-2 cm taller than evening height

Recommended Tools:

Portable Height MeterWall Height Sticker

Weight Measurement

Accurate weight measurement is fundamental for calculating BMI and body fat percentage.

  • Measure in the morning on an empty stomach, after using the bathroom
  • Wear light clothing, no shoes
  • Measure at the same time each day for consistency
  • Place the scale on a hard, flat surface, avoid carpets

Recommended Tools:

smart.weight.scaleBody Fat Scale

Waist Measurement

Waist circumference is a key parameter for body fat calculation, accurate measurement is crucial.

  • Stand relaxed with feet shoulder-width apart
  • Find your navel and measure at that level
  • The tape should touch the skin but not be tight
  • Breathe normally during measurement, don't hold in or push out your stomach
  • Morning measurement on an empty stomach is more accurate

Recommended Tools:

body.measuring.tapeautomatic.retractable.tape

Data sources and how we verify them

Every cut-point, band and formula on this page is taken from the issuing authority's own document, listed below. We do not use second-hand summaries, and we do not fill gaps with numbers no source states.

Cut-points are population-level statistical thresholds, not individual diagnoses. If your value sits near a category line, measure your waist as well and read it alongside body-fat percentage. Last checked: 2026-09-15.

References

  1. World Health Organization. Obesity and overweight (fact sheet). Geneva: WHO https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
  2. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163 PMID 14726171. https://pubmed.ncbi.nlm.nih.gov/14726171/
  3. WHO Western Pacific Regional Office, IASO, IOTF. The Asia-Pacific Perspective: Redefining Obesity and Its Treatment. Sydney: Health Communications Australia; 2000 https://apps.who.int/iris/handle/10665/206936
  4. 中华人民共和国国家卫生和计划生育委员会. WS/T 428—2013《成人体重判定》(Criteria of weight for adults). 北京：中国标准出版社，2013（2013-04-18 发布，2013-10-01 实施） 行业标准 WS/T 428—2013. https://www.nhc.gov.cn/ewebeditor/uploadfile/2013/08/20130808135715967.pdf
  5. 国家卫生健康委员会. 《成人肥胖食养指南（2024年版）》. 北京：国家卫生健康委员会，2024 https://www.nhc.gov.cn/sps/c100088/202402/9ba512ba8e314a47a181db11d2fa188d/files/1743476136267_20714.pdf
  6. Keys A, Fidanza F, Karvonen MJ, Kimura N, Taylor HL. Indices of relative weight and obesity. J Chronic Dis. 1972;25(6):329–343 PMID 4650929. https://pubmed.ncbi.nlm.nih.gov/4650929/
  7. National Institute for Health and Care Excellence (NICE). Overweight and obesity management — NICE guideline NG246, recommendations 1.9.11–1.9.15. London: NICE https://www.nice.org.uk/guidance/ng246/chapter/Identifying-and-assessing-
  8. American Diabetes Association. Standards of Care in Diabetes—2026: adult overweight and obesity screening, diagnosis and staging. Diabetes Care. 2026 https://professional.diabetes.org/standards-of-care
  9. Centers for Disease Control and Prevention. Adult BMI calculator — category ranges. Atlanta: US CDC https://www.cdc.gov/bmi/adult-calculator/

Each item above is a primary source we actually consulted. If you find a figure that disagrees with the original document, tell us — we will check it and correct it.

Health Information Disclaimer

Content on this site is for general information only and does not constitute medical advice. Consult a doctor or qualified health professional for personal health concerns. Last updated: August 9, 2026.

We do not keep your information. Height, weight, waist and age are calculated entirely in your browser — nothing is uploaded to our servers, logged or stored, and the numbers are gone as soon as you close or refresh the page. We measure anonymous traffic only, never the values you type. Full detail in our Privacy Policy.

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