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How to Calculate Your Ideal Weight

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Short answer

Ideal weight formulas add a fixed weight for every inch your height is over 5 ft (152.4 cm). The most used, the Devine formula, is 45.5 kg + 2.3 kg per inch over 5 ft for women. For example, a woman of 165 cm has a Devine ideal weight of 56.9 kg. This is general information, not medical advice.

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Formula

inches over 5 ft = height (cm) / 2.54 − 60

ideal weight = base weight + weight per inch × inches over 5 ft

  • height: your height in centimetres. One inch is 2.54 cm; 60 inches is 5 ft, or 152.4 cm.
  • inches over 5 ft: how many inches your height is above 152.4 cm
  • base weight and weight per inch: the constants of each formula, by sex
Formula Men Women
Devine (1974) 50 + 2.3 × inches over 5 ft 45.5 + 2.3 × inches over 5 ft
Robinson (1983) 52 + 1.9 × inches over 5 ft 49 + 1.7 × inches over 5 ft
Miller (1983) 56.2 + 1.41 × inches over 5 ft 53.1 + 1.36 × inches over 5 ft
Hamwi (1964) 48 + 2.7 × inches over 5 ft 45.5 + 2.2 × inches over 5 ft

The constants are the kilogram forms collected by Pai and Paloucek (2000). Results are rounded to 0.1 kg.

Step-by-step example

A woman of 165 cm:

  1. Inches over 5 ft: 165 / 2.54 − 60 = 4.96 inches.
  2. Devine: 45.5 + 2.3 × 4.96 = 56.9 kg.
  3. Robinson: 49 + 1.7 × 4.96 = 57.4 kg.
  4. Miller: 53.1 + 1.36 × 4.96 = 59.8 kg.
  5. Hamwi: 45.5 + 2.2 × 4.96 = 56.4 kg.
  6. Healthy weight range (BMI 18.5–24.9): from 18.5 × 1.65² = 50.4 kg to 24.9 × 1.65² = 67.8 kg.

Why the formulas give different results

Each formula came from different data and adds a different weight per inch. The gap grows with height:

Woman, 165 cm Man, 178 cm
Devine 56.9 kg 73.2 kg
Robinson 57.4 kg 71.1 kg
Miller 59.8 kg 70.4 kg
Hamwi 56.4 kg 75.2 kg
Healthy weight range 50.4–67.8 kg 58.6–78.9 kg

No single formula is right. Devine is the one most used in clinical practice, where it helps to dose medicines. Ideal weight is not a target weight.

Ideal weight and the healthy weight range

The ideal weight formulas give one value from height and sex only. The healthy weight range is the weights that keep your body mass index between 18.5 and 24.9, and it works for any height. The formulas are not defined below 152.4 cm (BDA PENG, 2022); use the healthy weight range there. The formulas ignore muscle and bone build, age and ethnic background. Ask your doctor about a target weight.

Worked example: A woman of 165 cm

Ideal weight (Devine)

56.9 kg

Ideal weight (Robinson)
57.4 kg
Ideal weight (Miller)
59.8 kg
Ideal weight (Hamwi)
56.4 kg
Healthy weight range: from
50.4 kg
Healthy weight range: to
67.8 kg
Step by step

  1. inches over 5 ft = height / 2.54 − 60

    inches over 5 ft = 165 / 2.54 − 60 = 4.96 in

  2. Ideal weight (Devine)

    Devine = 45.5 + 2.3 × inches over 5 ft

    Devine = 45.5 + 2.3 × 4.96 = 56.9 kg

  3. Ideal weight (Robinson)

    Robinson = 49 + 1.7 × inches over 5 ft

    Robinson = 49 + 1.7 × 4.96 = 57.4 kg

  4. Ideal weight (Miller)

    Miller = 53.1 + 1.36 × inches over 5 ft

    Miller = 53.1 + 1.36 × 4.96 = 59.8 kg

  5. Ideal weight (Hamwi)

    Hamwi = 45.5 + 2.2 × inches over 5 ft

    Hamwi = 45.5 + 2.2 × 4.96 = 56.4 kg

  6. Healthy weight range: from

    weight at BMI 18.5 = 18.5 × height²

    weight at BMI 18.5 = 18.5 × 1.65² = 50.4 kg

  7. Healthy weight range: to

    weight at BMI 24.9 = 24.9 × height²

    weight at BMI 24.9 = 24.9 × 1.65² = 67.8 kg

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