What Is Ideal Body Weight?
Ideal body weight (IBW) is an estimate of a healthy weight for a person based on their height and biological sex. The concept dates back to 1871, when French surgeon Pierre Broca wrote in his book "Memoires d'anthropologie" that a simple method to calculate IBW is by subtracting 100 from a patient's height in centimeters. That crude formula kicked off 150 years of refinement.
The formulas used today were originally developed by physicians for drug dosing calculations. When administering certain medications, dosing based on total body weight can lead to dangerous overdoses in patients carrying excess adipose tissue. IBW formulas give clinicians a safer reference point. A 2023 study published in the Journal of Intensive Care Society found that variability between different IBW formulas can produce results differing by up to 10% for the same patient, which has real implications for drug dosing in intensive care settings.
Outside of clinical settings, IBW is used as a general health reference. It gives you a rough idea of what a reasonable weight target looks like for your height. But these formulas produce estimates, not precise targets. A person's optimal weight depends on muscle mass, bone structure, age, activity level, and overall health. None of these variables are captured by the formulas. For a broader health assessment, pair IBW with our BMI Calculator and Body Fat Calculator to get a more complete picture.
What This Calculator Does
This calculator computes your ideal body weight using four widely referenced formulas: Devine, Robinson, Miller, and Hamwi. It presents each result side by side along with an average, giving you a useful range rather than a single number.
Inputs Required
- Biological Sex: Male or female (formulas use different base values for each)
- Height: In feet and inches (imperial) or centimeters (metric)
Outputs Provided
- Ideal Weight per Formula: Results from Devine, Robinson, Miller, and Hamwi formulas
- Average Ideal Weight: The average across all four formulas
How the Calculation Works
All four formulas use height above 5 feet as the key variable. Each adds a fixed weight per inch of height above 60 inches, starting from a base weight. The formulas were developed between 1964 and 1983, and each was derived from different population data and clinical goals.
Devine Formula (1974)
Male: 50 kg + 2.3 kg per inch over 5 feet
Female: 45.5 kg + 2.3 kg per inch over 5 feet
Dr. B.J. Devine published this formula in 1974 for use in clinical pharmacology. It is the most widely cited IBW formula in medical literature and appears in drug dosing references worldwide. The Devine formula was originally based on estimates of ideal body weight rather than population studies, which is a known limitation.
Robinson Formula (1983)
Male: 52 kg + 1.9 kg per inch over 5 feet
Female: 49 kg + 1.7 kg per inch over 5 feet
The Robinson formula was developed as a refinement of the Devine formula, using a larger population dataset. It produces slightly lower weight estimates for taller individuals.
Miller Formula (1983)
Male: 56.2 kg + 1.41 kg per inch over 5 feet
Female: 53.1 kg + 1.36 kg per inch over 5 feet
Published the same year as Robinson, the Miller formula uses a higher base weight but a smaller per-inch increment. It tends to produce the lowest estimates of the four formulas for very tall individuals.
Hamwi Formula (1964)
Male: 106 lbs + 6 lbs per inch over 5 feet
Female: 100 lbs + 5 lbs per inch over 5 feet
The Hamwi formula is the oldest of the four and the only one originally published in pounds. It was developed for nutritional assessment purposes and tends to produce higher estimates than the metric formulas, particularly for shorter individuals.
How to Use the Calculator
- Select imperial or metric units
- Select your biological sex (this affects the base weight in each formula)
- Enter your height using the sliders
- View your ideal weight from all four formulas and their average
- Use the range, not a single number, as your reference point
Example Calculations
Example 1: Male at 5 Feet 10 Inches
A male who is 5 feet 10 inches tall is 10 inches over 5 feet:
- Devine: 50 + (2.3 x 10) = 73 kg (161 lbs)
- Robinson: 52 + (1.9 x 10) = 71 kg (157 lbs)
- Miller: 56.2 + (1.41 x 10) = 70.3 kg (155 lbs)
- Hamwi: 106 + (6 x 10) = 166 lbs (75.3 kg)
- Average: approximately 160 lbs (72.5 kg)
The spread between the lowest and highest estimate is 11 pounds. That range is normal and reflects the different populations each formula was derived from.
Example 2: Female at 5 Feet 4 Inches
A female who is 5 feet 4 inches tall is 4 inches over 5 feet:
- Devine: 45.5 + (2.3 x 4) = 54.7 kg (121 lbs)
- Robinson: 49 + (1.7 x 4) = 55.8 kg (123 lbs)
- Miller: 53.1 + (1.36 x 4) = 58.5 kg (129 lbs)
- Hamwi: 100 + (5 x 4) = 120 lbs (54.4 kg)
- Average: approximately 123 lbs (56 kg)
Real World Scenarios
Clinical Drug Dosing in the ICU
Dr. Patel, an intensivist at a regional hospital, needs to calculate the dose of a weight-sensitive medication for a patient who is 5 feet 6 inches and weighs 210 lbs. Using total body weight would result in a dangerously high dose for certain drugs with narrow therapeutic windows. She uses the Devine formula to find the patient's IBW of approximately 125 lbs and doses the medication based on that figure. This is the original purpose these formulas were designed for, and it remains their most important clinical application.
Setting a Realistic Weight Loss Target
Jennifer weighs 225 lbs at 5 feet 7 inches. She has been trying to lose weight for two years and keeps setting goals based on what she sees on social media, targeting 130 lbs. The ideal weight calculator shows her IBW range is 134 to 147 lbs, with an average of about 140 lbs. This gives her a more grounded target. She also checks her BMI and sees that a weight of 145 lbs puts her at a BMI of 22.7, squarely in the healthy range. The IBW range helps her stop chasing an unrealistic number and focus on a sustainable goal.
Athletic Assessment and the Muscle Mass Problem
Marcus is a 5 feet 9 inch powerlifter who weighs 195 lbs at 12% body fat. The IBW calculator gives him an average ideal weight of about 156 lbs. By IBW standards, he is 39 lbs "overweight." But his lean body mass is approximately 172 lbs, which already exceeds the IBW estimate. This highlights the fundamental limitation of IBW formulas: they do not account for muscle mass. For athletes and heavily muscled individuals, IBW is not a useful metric. Body fat percentage is a far better indicator of health in these cases.
Common Mistakes to Avoid
- Treating one formula as definitive: Each formula was developed for a specific clinical purpose using different population data. The average of all four gives a more balanced estimate than any single formula alone
- Ignoring body composition: A heavily muscular person may weigh 30+ lbs more than the ideal weight range and still be in excellent health. IBW does not distinguish between muscle and fat
- Applying adult formulas to children: These formulas are validated for adults. Different methods, including BMI-for-age percentiles, apply to pediatric populations
- Using IBW as your only health measure: Pair this with BMI, body fat percentage, and advice from your healthcare provider for a complete picture. No single number tells the whole story
- Forgetting the formulas stop at 5 feet: For individuals shorter than 5 feet, the formulas produce unreliable results because they use height above 60 inches as their variable. A shorter person may get an artificially low estimate
Limitations of This Calculator
These formulas were developed decades ago using limited population data, primarily from Western populations. They do not account for ethnic differences in body composition, which research has shown to be significant. A 2016 study published in the American Journal of Clinical Nutrition found that Asian populations tend to have higher body fat percentages at the same BMI compared to Caucasian populations, while Black populations tend to have lower body fat at the same BMI. The IBW formulas do not adjust for these differences.
The formulas also assume a medium frame size. People with large frames (broad shoulders, thick wrists) may reasonably weigh 10% above the IBW estimate, while those with small frames may reasonably weigh 10% below it. This calculator does not adjust for frame size. For a more personalized assessment, consult a registered dietitian or physician who can evaluate your body composition directly.
Authoritative Research & Resources
- Variability in Ideal Body Weight Formulae (NIH/PMC) - A 2023 study published in the Journal of Intensive Care Society comparing IBW formulas and analyzing their variability in clinical settings. The study found that different formulas can produce results differing by up to 10% for the same patient, with implications for drug dosing safety.
- CDC - Assessing Your Weight - The Centers for Disease Control and Prevention's guide to healthy weight assessment, including BMI guidelines and the limitations of weight-only metrics. Useful for understanding how IBW fits alongside other health assessment tools.
- Universal Equation for Estimating Ideal Body Weight (PubMed/NIH) - A 2016 research paper proposing a universal IBW equation that integrates with BMI calculations, addressing some of the limitations of the older Devine, Robinson, Miller, and Hamwi formulas.