What Is Ideal Body Weight?
Ideal body weight (IBW) is an estimated weight range that is associated with the lowest risk of weight-related health problems for a given height. The concept originated in the insurance industry in the early 20th century when Metropolitan Life Insurance Company published tables linking height to the weight ranges that correlated with the lowest mortality rates among their policyholders. Since then, researchers have developed several mathematical formulas to estimate IBW based on height and sex.
It is important to understand that "ideal weight" is a clinical estimate, not a definitive verdict on what you should weigh. These formulas do not account for muscle mass, bone density, body composition, ethnicity, or age — all of which significantly influence what a healthy weight looks like for any individual. A professional bodybuilder at 5'10" might weigh 220 lbs with 8% body fat — well above any IBW formula result — while being in excellent health.
The formulas are most useful as starting reference points for clinical applications such as drug dosing (many medications are dosed based on IBW rather than actual weight), ventilator settings in hospitals, and nutritional assessments. For personal health goals, combining IBW with your BMI and body fat percentage gives a much more complete picture than any single metric.
The Four Ideal Weight Formulas Explained
This calculator uses four scientifically published formulas, each developed by different researchers at different times. All four use height and sex as inputs, with calculations based on inches above 5 feet (60 inches). Here is how each formula works:
Hamwi Formula (1964)
Developed by Dr. G.J. Hamwi, this was one of the first widely adopted IBW formulas. It was originally published as a quick reference for dietitians.
Male: 48.0 kg + 2.7 kg per inch over 5 feet
Female: 45.5 kg + 2.2 kg per inch over 5 feet
Tends to give higher results for taller individuals. Often considered the least accurate of the four but is still widely referenced in dietetics textbooks.
Devine Formula (1974)
Created by Dr. B.J. Devine, originally intended for calculating medication dosages rather than for dietary purposes. It became widely used for IBW estimation despite not being designed for that purpose.
Male: 50.0 kg + 2.3 kg per inch over 5 feet
Female: 45.5 kg + 2.3 kg per inch over 5 feet
Widely used in medical settings for drug dosing. Can significantly underestimate ideal weight for taller people and overestimate for shorter people.
Robinson Formula (1983) — Recommended
Published by Dr. J.D. Robinson as a modification of the Devine formula, specifically to correct the systematic errors observed in the original. Robinson used updated Metropolitan Life Insurance data and adjusted for sex differences more carefully.
Male: 52.0 kg + 1.9 kg per inch over 5 feet
Female: 49.0 kg + 1.7 kg per inch over 5 feet
Generally considered the most balanced and widely applicable of the four formulas. Produces moderate results that fall between the extremes of the other equations.
Miller Formula (1983)
Also published in 1983 by Dr. D.R. Miller, independently of Robinson. Miller aimed to create a formula that better reflected contemporary body composition data.
Male: 56.2 kg + 1.41 kg per inch over 5 feet
Female: 53.1 kg + 1.36 kg per inch over 5 feet
Starts with a higher base weight but adds less per inch. This means it tends to give higher results for shorter people and lower results for taller people compared to other formulas.
No single formula is definitive. We recommend the Robinson formula as the most balanced, but showing all four helps you see the range of estimates and understand that "ideal weight" is not a single number but a zone. The BMI-based healthy range (18.5-24.9) often provides the most practical guidance because it is the standard used by the World Health Organization and most healthcare providers globally.
BMI vs. Ideal Weight: Understanding the Difference
Body Mass Index (BMI) and ideal body weight formulas approach the question of "healthy weight" from different angles. BMI is a ratio of weight to height squared, producing a single number that maps to risk categories. The IBW formulas produce a specific target weight. Both have strengths and limitations:
| Feature | BMI | Ideal Weight Formulas |
|---|---|---|
| Inputs | Height + weight | Height + sex |
| Output | Dimensionless ratio | Target weight (kg/lbs) |
| Accounts for sex? | No | Yes |
| Accounts for muscle? | No | No |
| Clinical use | Screening, risk assessment | Drug dosing, nutrition planning |
| Best for | Population-level assessment | Individual clinical targets |
For a comprehensive view of your body composition, use this calculator alongside the BMI calculator and body fat calculator. The BMI healthy range (18.5-24.9) shown in this calculator provides the broadest scientifically-backed weight range, while the individual formulas give more specific targets that can serve as reference points for goal setting.
Body Frame Size and Its Impact
One important factor that none of the four formulas account for is body frame size. People with larger skeletal frames naturally carry more bone mass and have larger joints, which means they typically weigh more at any given height than small-framed individuals — even at the same body fat percentage. The original Metropolitan Life Insurance tables included adjustments for frame size (small, medium, large), but this was dropped from the mathematical formulas for simplicity.
You can estimate your frame size using wrist circumference. Measure the circumference of your wrist at its narrowest point, just above the wrist bone, and compare to these ranges:
| Height | Small Frame | Medium Frame | Large Frame |
|---|---|---|---|
| Women under 5'2" | < 5.5" | 5.5"-5.75" | > 5.75" |
| Women 5'2"-5'5" | < 6.0" | 6.0"-6.25" | > 6.25" |
| Women over 5'5" | < 6.25" | 6.25"-6.5" | > 6.5" |
| Men over 5'5" | < 6.5" | 6.5"-7.5" | > 7.5" |
If you have a large frame, your ideal weight may be 10-15% higher than what the formulas suggest. If you have a small frame, it may be 10-15% lower. This is one reason why the BMI-based range (18.5-24.9), which spans a wider weight range, is often more practical than a single formula-derived number. Consider using the waist-to-hip ratio calculator for an additional body composition measure that accounts for fat distribution.
Healthy Weight Ranges by Height
The following table shows the healthy weight range (BMI 18.5-24.9) for common heights, along with the Robinson formula ideal weight for reference. These ranges give a much more realistic picture of healthy weight than any single number:
| Height | Healthy Range (lbs) | Healthy Range (kg) | Robinson IBW (M/F) |
|---|---|---|---|
| 5'0" (152 cm) | 97-128 lbs | 44-58 kg | 52 / 49 kg |
| 5'3" (160 cm) | 107-141 lbs | 49-64 kg | 58 / 54 kg |
| 5'6" (168 cm) | 118-155 lbs | 54-70 kg | 63 / 59 kg |
| 5'9" (175 cm) | 128-169 lbs | 58-77 kg | 69 / 64 kg |
| 6'0" (183 cm) | 140-184 lbs | 63-83 kg | 75 / 69 kg |
| 6'3" (191 cm) | 152-200 lbs | 69-91 kg | 80 / 74 kg |
Notice how the healthy BMI range spans about 30-50 lbs for most heights. This wide range exists because healthy bodies come in many shapes. Two people at 5'9" could both be healthy at 135 lbs and 165 lbs depending on muscle mass, frame size, and body composition. The formulas provide a midpoint estimate, but the range is where health truly lives.
Limitations of Ideal Weight Formulas
While ideal weight formulas are useful clinical tools, they have significant limitations that every user should understand:
No Body Composition Consideration
All four formulas produce the same result whether you have 10% body fat or 35% body fat. A muscular athlete and a sedentary person of the same height get identical "ideal" weights. For anyone who strength trains regularly, body fat percentage is a far more meaningful metric.
Age Not Factored In
The formulas give the same result for a 25-year-old and a 75-year-old. In reality, the relationship between weight and health outcomes changes with age. Research published in the American Journal of Clinical Nutrition suggests that slightly higher BMIs (25-27) may be protective in older adults.
Ethnicity Not Considered
These formulas were developed primarily from data on Caucasian populations. The WHO has noted that different ethnic groups face different health risks at different BMI levels. For example, Asian populations may face higher risks at lower BMIs, while some Pacific Islander populations may be healthy at higher BMIs.
Outdated Data Sources
The oldest formula (Hamwi) dates from 1964, and even the newest ones (Robinson, Miller) are from 1983. Population body composition has changed significantly since then. None of the formulas have been updated with contemporary data.
For a more complete assessment of your healthy weight, complement this calculator with your body fat percentage, BMI, and waist circumference. Use the calorie calculator to determine the right intake for reaching and maintaining your target weight sustainably.
How to Reach Your Ideal Weight Safely
If your current weight differs significantly from your ideal weight range, the path to getting there should be gradual and sustainable. Crash diets and extreme calorie restriction are counterproductive — they lead to muscle loss, metabolic slowdown, nutrient deficiencies, and rebound weight gain. Here are evidence-based guidelines:
Target a Moderate Deficit
Aim for a calorie deficit of 300-500 calories per day, which translates to approximately 0.5-1 lb of weight loss per week. This rate preserves muscle mass, keeps energy levels stable, and is sustainable for months. Use the calorie calculator to find your target intake.
Prioritize Protein
Consuming 1.6-2.2g of protein per kg of body weight per day helps preserve lean muscle mass during weight loss. Research consistently shows that higher protein intake during a deficit results in better body composition outcomes. Track your macros with the macro calculator.
Include Resistance Training
Strength training is the most effective way to preserve and build muscle during weight loss. Even 2-3 sessions per week with progressive overload makes a significant difference. This improves your final body composition so that when you reach your target weight, you look and feel better than if you had dieted alone.
Monitor Progress Beyond the Scale
Body weight fluctuates daily due to water retention, food volume, and glycogen stores. Weigh yourself at the same time each day (ideally morning, after using the bathroom, before eating) and use a weekly average. Also track waist circumference and how your clothes fit — these often reveal progress that the scale misses.
Remember that the number on the scale is just one data point. A person who weighs 5 lbs more than their "ideal weight" but has excellent blood pressure, blood sugar, cholesterol, good energy levels, and regular exercise habits is healthier than someone at their "ideal weight" who is sedentary and malnourished. Health is multidimensional, and weight is only one piece of the puzzle.
Body Composition: Beyond Ideal Weight
As fitness science has advanced, the focus has shifted from "ideal weight" to "ideal body composition." Body composition refers to the proportions of fat, muscle, bone, and water in your body. Two people can weigh exactly the same while having vastly different amounts of muscle and fat — and correspondingly different health profiles.
Healthy body fat ranges for adults are approximately 10-20% for men and 18-28% for women. These ranges support normal hormone function, immune health, and organ protection while keeping metabolic disease risk low. Athletes often target the lower end of these ranges, while the general population should aim for the middle.
To get the most actionable picture of your body, use multiple metrics together: check your body fat percentage, calculate your BMI, measure your waist-to-hip ratio, and compare against the ideal weight formulas on this page. When these metrics align and all fall within healthy ranges, you can be confident that your weight is right for your body — regardless of what any single formula says.