为什么体重指数（BMI）很重要
BMI是一个广泛使用的筛查工具，它有助于评估体成分和潜在的健康风险。虽然不是完美的，但它为理解您的体重状况和与医疗服务提供者讨论健康提供了一个良好的起点。
如何使用BMI计算器
- 1选择您偏好的单位制（公制或英制）
- 2请输入您的身高和体重，务必准确。
- 3立即获取您的体质指数（BMI）结果和分类
- 4查看您在BMI指数上的位置，并了解其含义
使用BMI结果的建议
请记住，BMI 只是一个健康指标。还应考虑其他因素，如肌肉量、年龄和整体健康状况。在使用 BMI 的同时，结合其他健康测量指标，并咨询医疗服务提供者进行全面的健康评估。
常见问题解答
在这里找到关于体质指数（BMI）的常见问题的答案，包括它是如何计算的、你的结果代表什么以及它在健康评估中的作用。了解BMI的局限性、健康体重范围，以及何时咨询医疗服务提供者。
BMI存在局限性。对于运动员、老年人或肌肉量较高的人来说，它可能不够准确。最好将其作为多个健康指标之一，而不是孤立使用。
咨询医疗保健提供者，他们可以评估您的整体健康状况，考虑其他因素，并为您提供个性化建议，以达到或保持健康体重。
The WHO adult categories are the same for men and women: 18.5–24.9 is classified as normal weight. After menopause, fat distribution and muscle mass change, so BMI can over- or under-estimate risk. Waist circumference, blood pressure, lipids and a clinician’s assessment add context that BMI alone cannot.
Often not. BMI cannot tell fat from muscle. A strength athlete can land in the overweight or obese category with a low body-fat percentage. Use a body-fat or lean-mass estimate alongside BMI, and treat the number as a screening tool rather than a diagnosis.
If your weight is stable, once or twice a year is enough. During a planned weight change, monthly checks show trend better than daily ones. BMI moves only when height or weight moves — height is effectively fixed in adults — so weigh yourself the same way each time.
Not with adult cut-offs. Children and teens are assessed with age- and sex-specific BMI percentiles (CDC or WHO growth charts). This calculator uses adult WHO categories and should not be used to classify anyone under 18.
It is cheap, repeatable and, at population scale, correlates with cardiometabolic risk. It is a screening starting point, not a complete picture of health. That is why this page also explains limitations and links to body-fat and lean-mass tools.
WHO classifies 30.0–34.9 as Obesity Class I, 35.0–39.9 as Class II, and 40.0 or above as Class III. These are categories, not diagnoses. Individual risk depends on fat distribution, fitness, labs and medical history.
BMI already accounts for height (weight divided by height squared). Short and tall adults use the same categories. The formula can still mis-rank people with unusual limb-to-torso proportions or high muscle mass.
Use whichever you measure in. Metric is kilograms and centimetres; imperial is pounds and inches. Mixing systems is the most common source of a wildly wrong result.
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了解您的体质指数 (BMI)
使用您的BMI结果作为了解您身体构成的起点。记得要关注整体健康，包括均衡的营养和定期的体育活动。
How BMI is calculated
Body Mass Index is weight in kilograms divided by height in metres squared (kg/m²). In imperial units the same relationship is 703 × lb / in². The World Health Organization uses this index to define adult underweight, normal weight, overweight and three obesity classes.
The formula is simple on purpose. It was never meant to be a complete health exam. It does not know your training history, waist size, blood pressure or family risk. Use it as a first look, then read it next to those other facts.
What the WHO categories mean
Under 18.5 is classified as underweight; 18.5–24.9 as normal weight; 25.0–29.9 as overweight; 30.0 and above as obese, with further class breaks at 35 and 40. These cut-offs are for adults. Children need age- and sex-specific percentiles instead.
Categories describe groups, not destinies. Two people in the same band can have very different metabolic health. That is why this site also offers body-fat and lean-mass calculators rather than stopping at a single index.
When BMI misleads
High muscle mass, oedema, pregnancy, amputations, and some ethnic differences in fat distribution all weaken BMI as a solo metric. Older adults can lose muscle and keep a “normal” BMI while sarcopenia develops. If the number will change a medical decision, get a clinician involved rather than treating this page as a verdict.
Formula source: Quetelet Index (Body Mass Index) — World Health Organization