BMI計算機
身長と体重からBMIを算出します
What is BMI and how do you calculate it?
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in meters squared: BMI = kg/m². A BMI of 18.5-24.9 is considered normal weight. Below 18.5 is underweight, 25-29.9 is overweight, and 30+ is obese.
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Create Free AccountBMIとは？
BMI（Body Mass Index：体格指数）は、身長と体重から算出される肥満度を表す指標です。体重(kg)を身長(m)の2乗で割って計算します。体脂肪を直接測るものではありませんが、自分の体重が健康的な範囲かどうかを知る目安として世界中で広く使われています。
BMIの計算方法
計算式は「BMI = 体重(kg) ÷ 身長(m)²」です。結果は以下のように判定されます：18.5未満（やせ）、18.5〜24.9（標準）、25〜29.9（やや肥満）、30以上（肥満）。ただし、これはあくまで目安です。筋肉量が多い人はBMIが高くなりやすいなど、個人差があることも覚えておきましょう。
BMIの注意点
BMIは便利な指標ですが、万能ではありません。筋肉と脂肪を区別できないため、筋トレをしている人は健康でもBMIが高く出ることがあります。また、年齢・性別・体脂肪の分布なども考慮されていません。より正確に健康状態を把握するには、ウエスト周囲径や体脂肪率なども併せてチェックしましょう。
BMI vs BMR: What's the Difference?
BMI measures your weight relative to height to categorize your body size. BMR measures the calories your body burns at rest. BMI tells you if you're at a healthy weight; BMR tells you how much energy your body needs. Use both together for a complete picture of your health.
Frequently Asked Questions
What is a healthy BMI range?
A healthy BMI range is between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health problems. However, BMI is just one indicator and should be considered alongside other health markers.
Is BMI accurate for athletes and muscular people?
BMI can overestimate body fat in athletes and muscular individuals because it doesn't distinguish between muscle and fat mass. If you have significant muscle mass, consider using body fat percentage measurements for a more accurate assessment.
How often should I check my BMI?
Checking your BMI monthly is sufficient for most people. Since BMI changes gradually with weight changes, weekly checks are unnecessary. Focus on long-term trends rather than daily fluctuations.
What should I do if my BMI is too high or too low?
If your BMI falls outside the normal range, consult a healthcare professional. For high BMI, focus on a balanced diet and regular exercise. For low BMI, ensure adequate nutrition and caloric intake. A personalized workout plan can help you reach a healthy weight.
Does BMI differ by age and gender?
Standard BMI categories apply to adults aged 20 and older regardless of gender. For children and teens, BMI is calculated the same way but interpreted using age- and sex-specific percentiles. Older adults may have slightly different healthy ranges.