健康・フィットネス

理想体重計算機

身長と性別に基づく理想体重を計算

使い方
  1. Select your Gender.
  2. Enter your 身長 in cm.
  3. Click Calculate Ideal Weight to see your recommended weight according to four established medical formulas.

計算式

This calculator uses four widely recognized formulas for calculating Ideal Body Weight (IBW). It then averages them for a balanced recommendation.

  • Devine (1974): Widely used in medical settings for drug dosing.
  • Robinson (1983): A modification of Devine.
  • Miller (1983): A newer modification of Devine.
  • Hamwi (1964): Originally created to provide a simple rule of thumb.

Note: These formulas are intended for adults over 150cm (5ft). They do not account for muscle mass or body frame size.

What Is Ideal Body Weight (IBW) and Why Calculate It?

Ideal Body Weight (IBW) is a clinically established estimate of the weight at which a person of a given height and sex tends to have the best health outcomes and lowest disease risk. Unlike BMI, which classifies weight categories as a continuous scale, IBW formulas provide a single target weight range that has historically been used for medication dosing, anesthesia calculations, ventilator settings, and nutritional assessments in clinical medicine.

While no single number can perfectly define the "ideal" weight for every individual—since body frame, muscle mass, age, and ethnicity all play a role—IBW formulas offer a useful benchmark grounded in decades of medical research. Our calculator presents results from four validated formulas and their average, giving a well-rounded target range rather than a single potentially misleading figure.

The Four Ideal Weight Formulas Explained

🧪
Devine Formula (1974) — Originally created for predicting creatinine clearance in kidney disease patients, the Devine formula became the most widely adopted IBW equation in clinical practice, especially for drug dosing calculations. Men: 50 + 2.3 × (inches over 5 ft). Women: 45.5 + 2.3 × (inches over 5 ft).
🔬
Robinson Formula (1983) — A refinement of the Devine equation using actuarial insurance data. Produces slightly lower estimates for men and slightly higher for women compared to Devine.
📊
Miller Formula (1983) — Developed simultaneously with Robinson, using a different dataset. Tends to predict higher IBW for taller individuals and is considered by some researchers to be more appropriate for contemporary populations with higher average heights.
🏥
Hamwi Formula (1964) — The oldest formula in common use, designed as a simple "rule of thumb" for clinical staff. Men: 48 kg for the first 5 ft, then +2.7 kg per inch. Women: 45.5 kg for the first 5 ft, then +2.2 kg per inch.

All four formulas are intended for adults taller than 150 cm (approximately 5 ft) and become less reliable at extreme heights. The Wikipedia article on Ideal Body Weight provides a detailed comparative analysis of each formula's derivation and applications.

Body Frame Size: The Missing Variable

One limitation shared by all four IBW formulas is that they do not account for body frame size. People with larger skeletal frames naturally carry more bone and tendon mass, making a higher body weight appropriate. A practical way to estimate your frame size is the wrist circumference method:

📏
For women 5'2" and under: Small <5.5", Medium 5.5–5.75", Large >5.75"
For women 5'2"–5'5": Small <6", Medium 6–6.25", Large >6.25"
For men: Small <6.5", Medium 6.5–7.5", Large >7.5"
Adjust your IBW target up or down by 10% for large or small frames respectively.

IBW vs. Healthy BMI Weight Range: Which Should I Use?

Both IBW and BMI-based healthy weight ranges are useful but answer slightly different questions:

🎯
Ideal Body Weight — A single target number used primarily in clinical and pharmacological settings. Best for drug dosing, anesthesia, and ventilation calculations. Less nuanced for fitness goals.
📈
BMI Healthy Range (18.5–24.9) — A weight range correlated with lowest statistical health risk. For a 175 cm person, this translates to 56.7–76.3 kg—a span of ~20 kg, much broader than any single IBW formula. Use our BMI計算機 to see your healthy weight range.

For most individuals pursuing fitness or health goals, the BMI healthy weight range is more practical. IBW is most relevant in medical or pharmaceutical contexts. Pairing both with body fat percentage provides the most complete picture.

Frequently Asked Questions

Why do the four formulas give different results?

Each formula was derived from a different population dataset in a different era, using slightly different regression methods. The differences reflect genuine uncertainty about what constitutes the "optimal" weight—which is why we show all four and average them. The spread between formulas is typically 3–7 kg for most heights.

Are these formulas valid for children?

No. All four formulas are validated for adults over 150 cm and do not apply to children or adolescents, whose height-weight relationships change significantly with growth and sexual maturation. Pediatric weight assessments use age-and-sex-specific growth chart percentiles.

I'm very muscular. Is IBW relevant for me?

IBW formulas do not distinguish between fat and muscle. A muscular athlete may healthily weigh 10–20 kg above their calculated IBW due to greater lean mass. For such individuals, body fat percentage is a far more meaningful metric than IBW or BMI.

Related Health Calculators

⚖️
BMI計算機Weight status & healthy BMI range for your height
 📉
体脂肪率計算機Precise body composition using U.S. Navy method
 🔥
カロリー計算機Reach your target weight with daily calorie goals
 ⚡
基礎代謝計算機Your resting metabolic rate baseline

References & Further Reading

  1. Devine BJ. Gentamicin therapy. Drug Intelligence and Clinical Pharmacy, 1974.
  2. Robinson JD, et al. Estimating renal creatinine clearance from serum creatinine. Am J Hospital Pharm, 1983.
  3. Wikipedia contributors. Ideal Body Weight. Wikipedia, The Free Encyclopedia.
  4. Pai MP, et al. Drug dosing based on weight and body surface area. Pharmacotherapy, 2000.