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Ideal Body Weight

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Ideal Body Weight (IBW)

Ideal body weight is an estimated target weight based on height and sex, originally developed for medical dosing purposes and now commonly used as a general health reference.

Definition

Ideal body weight (IBW) is an estimated target weight calculated from a person's height and sex, originally developed in a clinical context to help estimate appropriate medication dosages rather than to define an aesthetic or fitness goal. Because certain drugs need to be dosed relative to body size, and using a patient's actual weight can be misleading for people who are significantly overweight or underweight, researchers created formulas that estimate a reference "ideal" weight from height alone. You can calculate yours with the Ideal Weight Calculator.

The most widely cited version is the Devine formula, published in 1974, which remains standard in many clinical dosing calculations today. Several other formulas — including Robinson, Miller, and Hamwi — were developed around the same era and produce similar, though not identical, results for the same height.

It's important to understand what ideal body weight does not measure: body composition. Two people can share the same height and calculated ideal body weight while having very different amounts of muscle and fat. For that reason, ideal body weight functions best as a general reference point, and is more informative when considered alongside body composition measures like lean body mass or body fat percentage.

Formula

The Devine formula:

  • Men: IBW = 50 kg + 2.3 kg × (height in inches over 60)
  • Women: IBW = 45.5 kg + 2.3 kg × (height in inches over 60)

"Height in inches over 60" means the number of inches taller than 5 feet (60 inches). For heights under 5 feet, the formula is typically not applied, or is adjusted downward proportionally.

Worked Example

A woman who is 5'6" (66 inches) tall:

Inches over 60 = 66 − 60 = 6

IBW = 45.5 + (2.3 × 6) = 45.5 + 13.8 = 59.3 kg (about 130.7 lb)

For a man at the same height of 5'6":

IBW = 50 + (2.3 × 6) = 50 + 13.8 = 63.8 kg (about 140.7 lb)

Key Things to Know

  • It ignores body composition entirely. Ideal body weight only uses height and sex, so it cannot tell the difference between a muscular frame and a higher body fat frame at the same weight — for a fuller picture, pair it with Lean Body Mass.
  • It was built for clinical dosing, not fitness goals. The Devine formula's origin in medication dosing means it prioritizes a consistent, predictable estimate over reflecting individual variation in build.
  • Multiple formulas exist and disagree slightly. Devine, Robinson, Miller, and Hamwi formulas can differ by a few kilograms for the same height, so don't treat any single number as exact.
  • It doesn't apply well to very short or very tall individuals. The linear per-inch adjustment becomes less reliable at the extremes of the height distribution, since it was calibrated against average-height populations.
  • Use it as a reference range, not a strict target. A healthy weight range is generally considered to span roughly 10% above or below calculated ideal body weight, rather than a single fixed number to hit.

Related Calculators

Ideal Weight Calculator →Find your ideal body weight and healthy weight range based on height and gender. Uses three medical formulas — Robinson, Miller, and Devine — for an accurate estimate. Free online calculator.

Related Terms

Lean Body MassLean Body Mass (LBM)

Frequently Asked Questions

The most widely used formula is the Devine formula, developed in 1974, which calculates ideal body weight from height alone using a different base and increment for men and women. It was originally created to help clinicians dose medications based on body size rather than as a general fitness target. The Ideal Weight Calculator applies this formula automatically based on your height and sex.
Not exactly. Ideal body weight formulas were designed for medical dosing calculations and only consider height and sex, while a truly healthy weight range depends on additional factors like muscle mass, frame size, and body fat distribution. Many people who are muscular or athletic weigh more than their calculated ideal body weight while still being perfectly healthy. It is best used as a general reference point rather than a strict target.
Formulas like Devine, Robinson, Miller, and Hamwi were each derived from different population datasets and studies conducted at different times, so they use slightly different base weights and per-inch increments. Differences between formulas for the same height are usually within a few kilograms. The Devine formula remains the most commonly cited in clinical settings.
No, ideal body weight formulas only use height and sex as inputs, so they cannot distinguish between someone who is muscular and someone who carries more body fat at the same weight. This is a key limitation, which is why lean body mass and body fat percentage are often considered alongside ideal body weight for a fuller picture. A bodybuilder may weigh well above their calculated ideal body weight while having very low body fat.
Many medications, particularly those with a narrow safety margin, are dosed based on body size because larger bodies distribute and metabolize drugs differently than smaller ones. Using actual body weight for very overweight patients can lead to overdosing, so clinicians developed ideal body weight formulas to estimate a more appropriate reference weight for dosing calculations. This clinical origin explains why the formula relies only on height and sex rather than body composition.