How ideal weight is calculated
The four classic ideal body weight (IBW) formulas all have the same shape: a base weight for someone exactly 5 feet (152.4 cm) tall, plus a fixed amount for every inch above that.
| Formula | Men | Women |
|---|---|---|
| Robinson (1983) | 52 kg + 1.9 kg per inch | 49 kg + 1.7 kg per inch |
| Miller (1983) | 56.2 kg + 1.41 kg per inch | 53.1 kg + 1.36 kg per inch |
| Devine (1974) | 50 kg + 2.3 kg per inch | 45.5 kg + 2.3 kg per inch |
| Hamwi (1964) | 48 kg + 2.7 kg per inch | 45.5 kg + 2.2 kg per inch |
Hamwi first wrote his rule in pounds: 106 lb plus 6 lb per inch for men and 100 lb plus 5 lb per inch for women. Devine’s formula was published to help dose a hospital antibiotic, and it is still the version most hospitals use when a drug dose depends on “ideal” weight. Robinson and Miller later refitted the idea to life-insurance height and weight tables. As a review in the Annals of Pharmacotherapy pointed out, none of the four was built from data linking weight to health.
The calculator also shows the healthy BMI range. The World Health Organization and the CDC class a body mass index of 18.5 to 24.9 as a healthy weight for adults. Turning that around gives a weight range for any height:
Worked examples
Example 1: a man 5 ft 10 in tall. He is 70 inches, 10 inches over 5 ft.
- Robinson: 52 + 1.9 × 10 = 71.0 kg (157 lb)
- Miller: 56.2 + 1.41 × 10 = 70.3 kg (155 lb)
- Devine: 50 + 2.3 × 10 = 73.0 kg (161 lb)
- Hamwi: 48 + 2.7 × 10 = 75.0 kg (165 lb)
The formulas agree within about 5 kg. The BMI range at 177.8 cm is much wider: 58.5 to 78.7 kg (129 to 174 lb).
Example 2: a woman 165 cm tall (5 ft 5 in). She is 5 inches over 5 ft. Robinson gives 57.5 kg, Miller 59.9 kg, Devine 57.0 kg and Hamwi 56.5 kg, so the formulas suggest about 56.5 to 59.9 kg (125 to 132 lb). Her healthy BMI range is 50.4 to 67.9 kg (111 to 150 lb).
Example 3: a woman 4 ft 10 in tall. She is 2 inches under 5 ft, so the calculator subtracts instead of adding. Devine gives 45.5 − 2.3 × 2 = 40.9 kg and Miller gives 50.4 kg, a wide spread that shows the formulas stretching past what they were made for. The BMI range of 40.2 to 54.0 kg (89 to 119 lb) is the better guide here.
Ideal weight chart
Ranges in pounds, rounded. The formula columns show the lowest and highest of the four formulas.
| Height | Women: formulas | Men: formulas | Healthy BMI range (both) |
|---|---|---|---|
| 5 ft 0 in (152 cm) | 100–117 lb | 106–124 lb | 95–127 lb |
| 5 ft 2 in (157 cm) | 110–123 lb | 118–130 lb | 101–136 lb |
| 5 ft 4 in (163 cm) | 120–129 lb | 130–136 lb | 108–145 lb |
| 5 ft 6 in (168 cm) | 129–135 lb | 140–143 lb | 115–154 lb |
| 5 ft 8 in (173 cm) | 138–141 lb | 148–153 lb | 122–164 lb |
| 5 ft 10 in (178 cm) | 146–151 lb | 155–165 lb | 129–174 lb |
| 6 ft 0 in (183 cm) | 153–161 lb | 161–177 lb | 136–184 lb |
| 6 ft 2 in (188 cm) | 159–171 lb | 167–189 lb | 144–194 lb |
| 6 ft 4 in (193 cm) | 165–181 lb | 174–201 lb | 152–205 lb |
Which number should you use?
- For general health, aim to be somewhere in the healthy BMI range. It is wide on purpose, because frame size, muscle and age all shift what is right for you.
- The formula results sit near the middle of that range. They are useful as a single, easy target, but being 5 kg above or below one is not a problem in itself.
- Frame size matters. A common rule of thumb with Hamwi is to take 10% off for a small frame and add 10% for a large one.
- Muscle changes the picture. Strength athletes often weigh more than every number here while being lean. The body fat calculator gives a better read on body composition.
Limits
These numbers are for adults. Children and teenagers need growth charts that account for age. Pregnancy, older age with muscle loss and some medical conditions also change what a healthy weight looks like, so ask a doctor if any of those apply.
Next steps
See where you are now with the BMI calculator. If you want to move toward a new weight, the calorie calculator gives a daily calorie target, and the protein calculator can use your ideal weight as the basis for a protein target. To switch between kilograms, pounds and stone, use the weight converter.