Ideal Body Weight (IBW)
Use the Ideal Body Weight (IBW) Calculator → Try the Ideal Body Weight (IBW) Quiz →Ideal Body Weight (IBW) is a clinical estimate of target weight based on height and sex, derived from the Devine, Robinson, Miller, and Hamwi formulas. It was originally developed for drug dosing, not fitness targets.
- Ideal body weight (IBW) was originally developed for pharmacokinetics (drug dosing), not as a personal weight goal; its use as a fitness target is a secondary application that has outgrown its original purpose.
- The Devine formula (1974) is the most widely used: 50 + 2.3 × (height in inches - 60) for men; 45.5 + 2.3 × (height in inches - 60) for women.
- The four major IBW formulas (Devine, Robinson, Miller, Hamwi) can differ by 5-10 kg for the same person - no formula is universally superior.
- IBW does not account for body composition, frame size, age, ethnicity, or fitness level; a muscular individual may be well above their IBW while in excellent health.
- For individual weight management, BMI combined with body fat percentage and waist circumference provides more meaningful personal targets than IBW alone.
What is Ideal Body Weight (IBW)?
Ideal body weight (IBW) is a clinically estimated target weight derived from height and gender, originally developed to guide drug dosing rather than to define an aesthetic or fitness goal. The most widely used formula is the Devine formula (1974): For men: $$\text{IBW} = 50 + 2.3 \times (\text{height in inches} - 60)$$ For women: $$\text{IBW} = 45.5 + 2.3 \times (\text{height in inches} - 60)$$
Several alternative formulas exist. The Robinson formula (1983) uses slightly different coefficients. The Miller formula (1983) produces lower estimates. The Hamwi formula (1964) is an older rule-of-thumb. All four formulas were empirically derived from population data and produce meaningfully different results, particularly at the extremes of height.
IBW was created for pharmacokinetic applications - specifically for calculating doses of renally-cleared and volume-of-distribution-sensitive drugs in patients where total body weight would lead to overdosing. Its use as a general weight target is a secondary application that has outgrown its original clinical purpose.
Ideal Body Weight (IBW) explained to a beginner
Ideal body weight gives you a rough target weight based only on your height and gender. A man who is 5'9" (175cm) has a Devine IBW of about 68.6 kg - but that number was originally invented by a doctor in 1974 to help calculate medication doses, not to define a fitness goal.
The important thing to understand is that IBW has no knowledge of how much of your weight is muscle versus fat. A muscular athlete at 80 kg and a sedentary person at 80 kg would both be equally "above their IBW" by 11 kg, but they have completely different health profiles. Use IBW as one rough reference point, not a hard target.
When to use Ideal Body Weight (IBW)
Use IBW as a reference baseline when calculating adjusted body weight for drug dosing in obese patients, or as a starting point for nutritional assessment in clinical settings. For general weight management, use IBW alongside BMI, body fat percentage, and waist circumference rather than as a precise personal target.
Worked examples for Ideal Body Weight (IBW)
This table quickly gives you the overview you need to understand Ideal Body Weight (IBW) and its most important comparisons.
| Height | Devine IBW (men) | Devine IBW (women) | Robinson IBW (men) | Robinson IBW (women) |
|---|---|---|---|---|
| 160 cm (5'3") | 54.9 kg | 50.4 kg | 56.4 kg | 53.1 kg |
| 170 cm (5'7") | 64.1 kg | 59.6 kg | 65.8 kg | 59.9 kg |
| 175 cm (5'9") | 68.6 kg | 64.1 kg | 70.5 kg | 63.3 kg |
| 183 cm (6'0") | 75.5 kg | 70.9 kg | 77.6 kg | 69.4 kg |
Common pitfalls
IBW formulas do not account for body composition, frame size, age, ethnicity, or fitness level. A muscular man at 175cm weighing 80kg is well above the Devine IBW of approximately 68kg but may be in excellent health. Conversely, someone meeting their IBW with low muscle mass and high fat may have significant metabolic risk despite being at their "ideal" weight.
Frequently asked questions about Ideal Body Weight (IBW)
How accurate is ideal body weight?
IBW formulas are empirical estimates with wide confidence intervals. Studies comparing the four major formulas find they can differ by 5–10kg for the same individual. IBW is most useful as a clinical dosing reference; it is a poor tool for individual weight goal-setting.
Which ideal body weight formula is best?
No formula is universally superior - the choice depends on the clinical context. The Devine formula remains the most widely used in clinical pharmacokinetics. For non-clinical purposes, BMI combined with body fat percentage provides more individually meaningful targets.
Why do different IBW formulas give different answers?
Each formula was developed from a different dataset using different reference populations. Devine (1974) was based on lung function research; Hamwi (1964) was a simple rule-of-thumb for diabetes management; Robinson and Miller (1983) re-analysed Metropolitan Life Insurance tables. Because they used different statistical methods and populations, they produce meaningfully different results.
Quiz: how well do you know ideal body weight?
1. What was Ideal Body Weight (IBW) originally developed for?
2. According to the FAQs, which IBW formula is most widely used in clinical pharmacokinetics?
3. According to the examples table, what is the Devine IBW for a 175cm (5'9") man?
4. What critical limitation do all IBW formulas share, according to the pitfalls section?
5. Why do the four major IBW formulas (Devine, Robinson, Miller, Hamwi) produce different results for the same person?