Ideal Body Weight: How to Calculate by Height and Frame
Ideal body weight (IBW) is an estimated weight range considered healthiest for a person based on their height and, in some models, their frame size. Clinicians use IBW formulas to dose medications, set ventilator parameters, and guide nutritional assessments. The four most common formulas — Devine, Hamwi, Robinson, and Miller — each produce a single target number, and they can differ by up to 19% for women and 14% for men of the same height.
Quick Answer
- 1. Devine formula (most used): men = 50 kg + 2.3 kg per inch over 5 ft; women = 45.5 kg + 2.3 kg per inch over 5 ft.
- 2. IBW results can differ by up to 14-19% across the four major formulas for the same height.
- 3. Frame size adjusts IBW by plus or minus 10% (small frame subtract 10%, large frame add 10%).
- 4. A healthy BMI range (18.5-24.9) provides a broader, often more practical, weight target.
Calculate your ideal body weight
Compare results from four science-based formulas adjusted for your height, sex, and frame size.
Calculate Ideal Weight FreeWhy Ideal Body Weight Matters
Ideal body weight is not about aesthetics or hitting a specific number on a scale. It exists because many medical decisions depend on a weight estimate that reflects lean body mass rather than total body weight. The Devine formula, published in 1974 in Drug Intelligence and Clinical Pharmacy, was originally developed to calculate gentamicin antibiotic dosing. It became the default IBW equation in clinical practice because it was simple, easy to memorize, and produced reasonable estimates for the drug dosing applications it was designed for.
Today, IBW formulas are used across medicine and nutrition. Respiratory therapists use them to set tidal volumes on ventilators (the ARDS Network protocol recommends 6-8 mL per kg of ideal body weight). Pharmacists use them for weight-based drug dosing. Dietitians use them as starting points for calorie and protein calculations. Understanding which formula is being used and why matters because the results can vary significantly.
The Four Major IBW Formulas
Each formula uses height as its primary input and provides separate equations for men and women. All assume a baseline height of 5 feet (60 inches) and add a fixed amount per inch above that threshold.
Hamwi Formula (1964)
The oldest of the four, introduced by Dr. G.J. Hamwi for use in nutritional counseling. It remains popular among dietitians.
- Men: 48 kg + 2.7 kg for each inch over 5 feet
- Women: 45.5 kg + 2.2 kg for each inch over 5 feet
Devine Formula (1974)
The most widely used formula in clinical medicine. Originally published for antibiotic dosing, it became the standard for ventilator settings and drug calculations.
- Men: 50 kg + 2.3 kg for each inch over 5 feet
- Women: 45.5 kg + 2.3 kg for each inch over 5 feet
Robinson Formula (1983)
Developed as a refinement of the Devine formula, Robinson tends to produce slightly higher estimates for men and more moderate estimates for women.
- Men: 52 kg + 1.9 kg for each inch over 5 feet
- Women: 49 kg + 1.7 kg for each inch over 5 feet
Miller Formula (1983)
The Miller formula produces the highest baseline values but adds less weight per inch, resulting in higher estimates for shorter people and more moderate values for taller people.
- Men: 56.2 kg + 1.41 kg for each inch over 5 feet
- Women: 53.1 kg + 1.36 kg for each inch over 5 feet
How Much Do the Formulas Differ?
A 2023 study published in BMC Anesthesiology found that the difference in IBW between the Devine formula and other formulas reaches up to 14% in males and 19% in females. For practical context, here is what the four formulas produce for a few common heights:
| Height | Devine | Hamwi | Robinson | Miller |
|---|---|---|---|---|
| 5'4" woman | 54.1 kg (119 lb) | 54.3 kg (120 lb) | 55.8 kg (123 lb) | 58.5 kg (129 lb) |
| 5'7" woman | 61.0 kg (134 lb) | 60.9 kg (134 lb) | 60.9 kg (134 lb) | 62.6 kg (138 lb) |
| 5'10" man | 73.0 kg (161 lb) | 75.0 kg (165 lb) | 71.0 kg (157 lb) | 70.3 kg (155 lb) |
| 6'0" man | 77.6 kg (171 lb) | 80.4 kg (177 lb) | 74.8 kg (165 lb) | 73.1 kg (161 lb) |
The variation means a 6-foot man could have an "ideal" weight anywhere from 161 to 177 pounds depending on which formula is used. This is a 16-pound spread, which underscores that IBW should be treated as a range, not a precise target.
Adjusting for Frame Size
Standard IBW formulas assume a medium frame. The traditional adjustment recommended by the American Dietetic Association is:
- Small frame: Subtract 10% from the IBW result.
- Medium frame: Use the formula result as-is.
- Large frame: Add 10% to the IBW result.
To determine your frame size, measure your wrist circumference and compare it to standard charts, or use the thumb-and-finger wrist test: if your thumb and index finger overlap when wrapped around your wrist, you likely have a small frame; just touching indicates medium; not touching indicates large.
IBW vs BMI: Which Should You Use?
Both IBW and BMI use height and weight, but they serve different purposes. BMI (Body Mass Index) provides a range of healthy weights: for a healthy BMI of 18.5 to 24.9, a 5-foot-10 person has an acceptable weight range from about 129 to 174 pounds. IBW formulas produce a single-point estimate within that range.
For most people assessing their own health, the BMI range is more practical because it acknowledges natural variation in body composition. IBW is more useful in clinical settings where a specific weight number is needed for calculations. Neither metric accounts for muscle mass, body fat percentage, or fat distribution, all of which matter for health outcomes.
Limitations of Ideal Body Weight Formulas
All four IBW formulas share several significant limitations that are important to understand:
- Height-only input: They ignore body composition, muscle mass, bone density, and fat distribution.
- Population averages: Formulas were developed using data from predominantly white populations in the mid-20th century and may not generalize well across all ethnicities and body types.
- No age adjustment: A 25-year-old and a 75-year-old of the same height get the same IBW, despite significant differences in body composition.
- Below 5 feet: All formulas use 5 feet as a baseline and are not validated for heights below 60 inches. Results for people under 5 feet tall should be interpreted with extra caution.
- Clinical origins: These formulas were designed for drug dosing and clinical assessments, not as personal health goals.
A Better Approach: Using IBW as One Data Point
Rather than fixating on any single IBW number, use it as one data point alongside other metrics:
- BMI range: Check whether your weight falls within the healthy BMI range of 18.5-24.9 using our BMI calculator.
- Body fat percentage: A more direct measure of body composition. Healthy ranges are 14-24% for men and 21-31% for women. Use our body fat calculator for an estimate.
- Waist circumference: Waist measurements above 40 inches for men or 35 inches for women are associated with increased health risks regardless of total body weight.
- Trend over time: How your weight is changing matters more than any single measurement.
The Bottom Line
Ideal body weight formulas provide a quick, height-based estimate of a healthy weight target. The Devine formula is the most widely used in clinical practice, but all four major formulas produce different results, varying by up to 14-19% for the same height. Frame size adjustments of plus or minus 10% add further variation. For personal health assessment, treat IBW as a general reference point and consider the full picture: BMI range, body fat percentage, waist circumference, and overall fitness.
Compare all four formulas instantly with our free ideal body weight calculator, or estimate your body composition with the body fat calculator.
Frequently Asked Questions
What is the most accurate ideal body weight formula?
No single formula is universally 'most accurate' because ideal body weight depends on body composition, frame size, and individual health factors that no height-based formula can fully capture. The Devine formula is the most widely used in clinical practice, particularly for drug dosing and ventilator settings. The Robinson formula tends to produce slightly higher values that some researchers consider more realistic for modern populations. For a general health assessment, using all four formulas and looking at the range they produce gives you a more useful picture than relying on any single number.
Does frame size affect ideal body weight?
Yes, frame size significantly affects what a healthy weight looks like. A person with a large frame naturally carries more bone and muscle mass, so their ideal weight is higher than someone of the same height with a small frame. The standard adjustment is plus or minus 10%: subtract 10% from the formula result for a small frame, and add 10% for a large frame. You can estimate your frame size by wrapping your thumb and index finger around your wrist. If they overlap, you have a small frame; if they just touch, medium; if they do not touch, large. More precisely, measure your elbow breadth and compare to frame size charts.
Why do ideal body weight formulas only use height?
The original IBW formulas were developed in the 1960s and 1970s for specific clinical purposes, not as comprehensive health assessments. The Devine formula (1974) was created for calculating antibiotic dosing, and the Hamwi formula (1964) was designed for quick nutritional assessments. Height was chosen as the sole variable because it is easy to measure accurately and correlates well enough with lean body mass for these clinical applications. For a more complete picture of healthy weight, consider body fat percentage, waist circumference, and BMI alongside IBW.
Is ideal body weight the same as a healthy BMI weight?
Not exactly. A healthy BMI (18.5 to 24.9) defines a broad range of acceptable weights for a given height. For a 5-foot-10 person, that range spans from about 129 to 174 pounds. Ideal body weight formulas produce a single number within that range, typically near the middle. Think of IBW as a midpoint estimate and the healthy BMI range as the full acceptable window. Both are useful reference points, but neither accounts for muscle mass, body fat distribution, or individual health conditions.
Should I use ideal body weight for calorie calculations?
IBW can be a useful starting point for setting calorie targets, especially if you are significantly over or under your target weight. Many dietitians use adjusted body weight (a blend of actual and ideal weight) for obese patients to avoid underfunding calorie needs. The common formula is: adjusted body weight = IBW + 0.25 to 0.4 multiplied by (actual weight minus IBW). For people within a healthy weight range, using actual body weight for TDEE and calorie calculations is typically more practical and accurate.
Find your ideal body weight
Enter your height, sex, and frame size to compare results from four science-based formulas.
Calculate Ideal Weight Free