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Body Fat Calculator

Calculate body fat percentage using the US Navy formula.

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Formula

体重より体脂肪率が重要な理由

米海軍式とBMI式の比較

健康的に体脂肪を減らす方法

体重が同じでも、体の組成は人によって大きく異なります。体脂肪率15%・除脂肪体重85%の人は、同じ体重で体脂肪率30%の人より代謝的に健康です。体脂肪率は健康リスク、フィットネスレベル、食事や運動プログラムの効果をより正確に把握できる指標です。

米海軍式は体の周囲径を測定する方法で、ほとんどの人にとってより正確です。BMIに基づくDeurenberg式は体重・身長・年齢・性別のみを使用するため精度は劣りますが、体の測定ができない場合に便利です。可能であれば海軍式を使用してください。

  • 適度なカロリー不足（1日300〜500 kcal）を維持する。極端な制限は筋肉量の減少を招きます。
  • 減量中の筋肉量を保つために、体重1kgあたり1.6〜2.2gのタンパク質を優先的に摂取する。
  • 脂肪を減らしながら筋肉を維持または増やすために、週3〜4日の筋力トレーニングを行う。
  • 体重の0.5〜1%/週のペースで減量する。これ以上速いペースだと除脂肪体重が失われます。

よくある質問

How is body fat percentage calculated?
This calculator offers two methods. The US Navy formula uses circumference measurements (waist, neck, and hip for women) along with height to estimate body fat using a logarithmic formula. The BMI-based Deurenberg formula uses BMI, age, and sex. Both are estimates — the gold standard is DEXA scan.
What is a healthy body fat percentage?
For men: 6–13% (athletes), 14–17% (fitness), 18–24% (acceptable). For women: 14–20% (athletes), 21–24% (fitness), 25–31% (acceptable). Below essential fat levels (men <5%, women <10%) is dangerous. Above obese thresholds (men >25%, women >32%) increases health risks.
How do I measure my waist accurately?
For the US Navy formula, measure your waist at the navel level while exhaling normally. Do not suck in or push out. Measure neck at the narrowest point, just below the Adam's apple. Women measure hips at the widest point across the buttocks.
How accurate is the US Navy formula?
The US Navy method has a margin of error of about ±3–4% compared to hydrostatic weighing. It is considered reasonably accurate for most people and is widely used by the military and fitness professionals. It may be less accurate for very muscular individuals or those with unusual body proportions.
What is lean body mass?
Lean body mass (LBM) is everything in your body except fat — muscles, bones, organs, water, and connective tissue. It is calculated as: LBM = Total Weight × (1 − body fat%). Increasing LBM through strength training raises your metabolic rate and improves body composition even without losing weight.

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