Enter Body Data
<18.5 Normal
18.5-23.9 Overweight
24-27.9 Obese
≥28
BMI Basics
What is BMI?
BMI (Body Mass Index) is a widely used international indicator for assessing body weight and health status. It evaluates whether a person's weight is in a healthy range based on the ratio of height to weight. BMI was proposed by Belgian mathematician Adolphe Quetelet in 1832 and has been widely adopted by the WHO and health organizations worldwide for nearly 200 years.
BMI Formula
Standard formula: BMI = weight(kg) ÷ height²(m)
Imperial formula: BMI = weight(lb) ÷ height²(in) × 703
Chinese BMI Classification
- ：BMI < 18.5 — Underweight, possible malnutrition or health risks
- ：BMI 18.5 - 23.9 — Healthy weight range, lowest disease risk
- ：BMI 24.0 - 27.9 — Overweight, watch diet and exercise
- ：BMI ≥ 28.0 — Obese, significantly increased risk of cardiovascular disease and diabetes
How to Use
This BMI calculator is simple and intuitive. Here is a detailed usage guide:
：First select Metric or Imperial based on your preference. Metric uses cm and kg (international standard); Imperial uses ft/in and lb (common in the US). After switching, input labels and results adapt automatically.
Weight：Enter your actual height (to one decimal place) and weight. If you don't know your exact weight, use recent health check data or home scale measurements. All calculations are done locally in the browser — no data is uploaded to any server, ensuring complete privacy.
：Entering age and gender provides more comprehensive results including BMR (Basal Metabolic Rate), daily calorie recommendations, and body fat estimation. These are optional — BMI can be calculated without them, but results will be more detailed with them.
View results：After clicking "Calculate BMI", the results area shows: BMI value, classification, visual gauge, ideal weight range, BMR, daily calorie recommendation, and body fat estimation. Each indicator has detailed interpretation to help you understand your body status.
Use Cases
BMI calculators are widely used in daily life. Here are typical use cases:
Daily health management: Regularly (e.g. monthly) using a BMI calculator to track weight trends is an effective way to manage healthy weight. Record each BMI value and date in a phone memo or health app to form a long-term tracking curve. When BMI approaches or exceeds 24, adjust diet and exercise plans promptly.
Fitness planning: Before starting a fitness plan, measure BMI to understand your baseline. Underweight people should focus on muscle gain with high-protein diet; overweight/obese people should prioritize fat loss, starting with low-intensity cardio and gradually increasing. Normal BMI people can balance muscle gain and body shaping.
Pre-employment health check: Some employers have implicit weight requirements (though weight discrimination is illegal, being overweight may affect physical fitness tests for certain positions). Use the BMI calculator 1-2 weeks before a health check to assess your status, and adjust through diet and exercise if needed.
Extended Knowledge
BMI limitations: Although BMI is the most widely used weight assessment indicator, it has clear limitations. BMI does not distinguish between muscle and fat mass, meaning muscular athletes (like bodybuilders, weightlifters) may be incorrectly classified as overweight or obese. Similarly, BMI cannot reflect fat distribution — abdominal fat (visceral fat) is more dangerous than subcutaneous fat, but BMI is insensitive to this.
BMR and TDEE: BMR (Basal Metabolic Rate) is the minimum calories needed to sustain life at rest, accounting for 60-75% of daily energy expenditure. TDEE (Total Daily Energy Expenditure) is BMR plus daily activity and exercise. This tool calculates BMR. For TDEE, multiply BMR by activity factor: sedentary ×1.2, light activity ×1.375, moderate activity ×1.55, heavy activity ×1.725.
Related health indicators: BMI，Weight：1）：Male ≥90cm、Female ≥85cm ；2）：Male >0.9、Female >0.85 ；3）：Male 10-20%、Female 20-30% ；4）：1-9 ，10 。 BMI 。
FAQ
What is BMI?
BMI (Body Mass Index) is an international standard indicator for measuring body weight status and health. Formula: BMI = weight(kg) ÷ height²(m). Normal range: 18.5-24.9.
What is the normal BMI range?
：BMI < 18.5，18.5-23.9，24.0-27.9，≥28.0。，18.5-24.9。
Is the BMI calculator accurate?
BMI is a reference indicator suitable for most adults, but has limitations: it doesn't distinguish muscle from fat, so athletes may be misclassified as overweight. Standard BMI is also not applicable to pregnant women, elderly, and children.
How to reach ideal weight?
To reach ideal weight: 1) Control calorie intake, eat more vegetables, fruits, and quality protein; 2) At least 150 minutes of moderate aerobic exercise per week; 3) Adequate sleep (7-9 hours); 4) Reduce sedentary time, increase daily activity; 5) Consult a nutritionist or doctor for a personalized plan if needed.
BMI vs body fat percentage?
BMI is calculated only from height and weight, unable to distinguish muscle from fat. Body fat percentage directly measures the proportion of fat in the body and is a more precise obesity indicator. For example, muscular athletes may show overweight BMI but normal body fat; conversely, some people have normal BMI but high body fat (called normal weight obesity).
Do BMI standards vary by age and gender?
Standard BMI applies to adults aged 18-65. For children and adolescents, age- and gender-specific BMI percentiles are needed. For elderly (65+), the normal BMI range can be slightly relaxed (23-28). BMI standards don't apply to pregnant and breastfeeding women.