Enter your height (feet/inches) and weight (pounds) to calculate your Ideal Body Weight.
Ideal Body Weight (IBW) is an estimate of the weight range associated with good health for a given height and sex. This ideal body weight calculator applies three established clinical formulas: the Devine, Robinson, and Hamwi methods to produce a range rather than a single number. The tool works for men, women, and pediatric patients. Enter your height and sex to calculate ideal body weight instantly.
(IBW is a clinical reference, not a body goal. Weight is one of many health markers. Always discuss weight-related health questions with a qualified clinician.)
How to Calculate Ideal Body Weight
All three IBW formulas share the same logic. Start from a base weight at exactly 5 feet (152.4 cm) and add a fixed amount per inch of height above that. The formulas differ in their base weight and per-inch increment, which is why they produce slightly different outputs for the same person.
Ben J. Devine introduced his formula in 1974 to help clinicians estimate drug dosages based on height and weight. It became the most widely cited ideal body weight calculation formula in clinical practice.
This is how to calculate ideal body weight step by step using the Devine method:
- Measure your height in feet and inches.
- Subtract 5 feet to get the number of inches above the base height.
- Multiply those inches by the formula's per-inch increment.
- Add the result to the formula's base weight for your sex.
The calculator applies all three formulas at once. You get a range rather than a single number, which is a more accurate representation of what ideal body weight calculation can and cannot tell you.
Ideal Body Weight Calculation Formulas
The three formulas below cover most clinical use cases. Each one applies the ideal body weight calculation formula as a linear function of height above 5 feet. All were originally derived in kilograms.
Devine Formula
Ben J. Devine published his formula in 1974. It became the most widely cited IBW formula in clinical practice. The per-inch increment is identical for men and women at 2.3 kg, but the base weights differ by sex.
| Sex | Formula |
|---|---|
| Male | 50 kg + 2.3 kg per inch above 5 ft |
| Female | 45.5 kg + 2.3 kg per inch above 5 ft |
Robinson Formula
The Robinson Formula was published in 1983 as a refinement of the Devine equation. It raises the male base weight to 52 kg and lowers the per-inch increment to 1.9 kg, producing a leaner estimate for taller men. The female base rises to 49 kg with a 1.7 kg increment. Robinson tends to give the lowest IBW of the three formulas for tall individuals.
| Sex | Formula |
|---|---|
| Male | 52 kg + 1.9 kg per inch above 5 ft |
| Female | 49 kg + 1.7 kg per inch above 5 ft |
Hamwi Formula
The Hamwi Formula is the oldest of the three, published in 1964. It uses a higher per-inch increment for men and tends to produce the largest IBW estimates for taller individuals. It remains common in dietetic and clinical nutrition practice.
| Sex | Formula |
|---|---|
| Male | 48 kg + 2.7 kg per inch above 5 ft |
| Female | 45.5 kg + 2.2 kg per inch above 5 ft |
Ideal Body Weight Calculator for Women
The ideal weight calculator for women applies lower base weights than the male versions of the same formulas. This reflects two biological realities. Women carry a higher proportion of body fat relative to lean mass. Women also have lower average bone density and muscle mass than men of the same height.
The Devine formula sets the female base at 45.5 kg against 50 kg for men. The Robinson formula raises the female base to 49 kg. The result is a lower IBW estimate at every height compared to the male calculation.
Female IBW example at 5 ft 5 in (165 cm):
- Devine: 57.7 kg (127 lb)
- Robinson: 56.2 kg (124 lb)
- Hamwi: 56.4 kg (124 lb)
- Healthy range across formulas: approximately 56 to 58 kg
Factors including frame size, muscle mass from training, and hormonal variation all influence what a healthy weight looks like for any individual woman. None of the formulas account for these variables. The female ideal body weight calculator result is a reference band, not a target to reach.
Ideal Body Weight Calculator for Men
The ideal body weight calculator for men produces higher estimates than the female version at every height. This reflects the greater average muscle mass and bone density in male bodies. Muscle weighs more than fat per unit volume, so a man and a woman at the same height can both be healthy while differing significantly in weight.
Male IBW example at 5 ft 10 in (178 cm):
- Devine: 73 kg (161 lb)
- Robinson: 71 kg (157 lb)
- Hamwi: 75 kg (165 lb)
- Healthy range across formulas: approximately 71 to 75 kg
Highly trained men who lift weights regularly will often sit above their IBW while carrying low body fat. In these cases, IBW is a less useful clinical reference than direct body composition measurement. The male ideal body weight calculation gives a useful starting point but does not replace a full health assessment.
Ideal Body Weight Calculator for Pediatrics
The adult IBW formulas do not apply to children. The ideal body weight calculator for pediatrics uses age- and height-based references instead, because children's bodies are still developing and their healthy weight range changes continuously as they grow.
The most common method for ideal body weight calculation in pediatrics uses height to estimate expected weight based on growth charts. In clinical practice, CDC growth charts and WHO Child Growth Standards are the reference standards for pediatric growth assessment. A child's IBW is typically taken as the weight corresponding to the 50th percentile for their height on the appropriate growth chart.
The calculator switches to this growth-chart method automatically when an age under 18 is entered. The result appears as a weight range rather than a single figure. For pediatric weight concerns, always work with a pediatrician. Growth tracking across multiple visits is more informative than any single measurement.
Adjusted Ideal Body Weight Calculator
The adjusted ideal body weight calculator applies in clinical settings for patients whose actual weight is more than 30% above their IBW. At that point, using IBW alone for drug dosing underestimates metabolic activity, because some excess fat tissue is still metabolically active. Adjusted Body Weight corrects for this.
Adjusted Body Weight formula:
Adjusted BW = IBW + 0.4 × (Actual Weight − IBW)
Worked example — actual weight 100 kg, Devine IBW 70 kg:
- = 70 + 0.4 × (100 − 70) = 70 + 12 = 82 kg
The 0.4 factor reflects the estimated metabolically active proportion of excess weight. Adjusted body weight is used most commonly in aminoglycoside antibiotic dosing, chemotherapy calculations, and renal dosing adjustments. It is not a weight target. It is a pharmacokinetic tool for clinical dosing decisions.
Percent Ideal Body Weight Calculation
To calculate percent ideal body weight, divide your actual weight by your IBW and multiply by 100. This shows how your current weight compares to the estimate as a percentage.
Percent IBW = (Actual Weight ÷ IBW) × 100
| Percent IBW | Weight status |
|---|---|
| Below 70% | Severely underweight |
| 70 to 89% | Underweight |
| 90 to 110% | Normal weight |
| 110 to 120% | Overweight |
| Above 120% | Obesity risk range |
Percent IBW is used in clinical nutrition assessments to flag patients who need nutritional intervention. A percent ideal body weight below 70% is associated with significant nutritional depletion. Scores above 120% are used as one threshold in obesity-related dosing decisions.
Healthy Weight Range
The healthy weight range sits around your IBW result, not at a single point. Because the three formulas produce slightly different figures for the same person, the spread between the lowest and highest result defines a practical healthy weight range. For most adults, this spread runs 3 to 5 kg across all three formulas.
Illustrative range — male, 5 ft 9 in (175 cm):
Ideal Body Weight vs BMI
Body Mass Index and Ideal Body Weight measure different things and answer different questions. BMI evaluates your weight category by dividing weight in kilograms by height in meters squared. It returns a category label: underweight, normal, overweight, or obese. Ideal body weight calculation, by contrast, gives an estimated weight to aim for rather than a category label.
| Measure | What it does | Main limitation |
|---|---|---|
| Ideal Body Weight | Estimates a target weight based on height and sex | Ignores body composition, frame size, and age |
| Body Mass Index | Classifies weight status using weight and height | Same limitations, plus does not adjust for sex differences in body composition |
Neither metric accounts for how weight is distributed between muscle, fat, and bone. A person with high muscle mass can show a normal IBW and a high BMI. A person with low muscle mass can show a normal BMI and sit above their IBW. For a full picture, both are best used alongside body composition data from a clinician.
Frequently Asked Questions
Scientific insights into your development
Ideal Body Weight (IBW) is a clinical estimate of the weight range associated with the lowest risk of chronic disease and best overall health outcomes for a given height and sex. It was originally developed to standardize drug dosing but is now used broadly in health and fitness contexts.
They are useful statistical estimates but have significant limitations. IBW formulas do not distinguish between muscle mass and body fat. A highly muscular athlete might weigh more than their "ideal" weight while being extremely healthy. They should be used as one of many health indicators, not the final word on your health status.
The Devine formula is the most widely used in medical settings. Robinson developed a slightly leaner model specifically for taller individuals. Hamwi is a more traditional formula often used in nutrition counseling. Most people find the best result by looking at the average range produced by all three.
Neither is perfect. BMI gives you a category (underweight, normal, etc.), while IBW gives you a specific target weight. IBW is often more intuitive for individuals, but like BMI, it cannot account for body composition (muscle vs. fat ratio).
Sources
- Devine BJ (1974). Gentamicin therapy. Drug Intelligence and Clinical Pharmacy.
- Robinson JD et al. (1983). Estimation of ideal body weight. American Journal of Hospital Pharmacy.
- Hamwi GJ (1964). Changing dietary concepts. In: Diabetes Mellitus: Diagnosis and Treatment. American Diabetes Association.
- CDC Growth Charts. Centers for Disease Control and Prevention.
- WHO Child Growth Standards. World Health Organization.