Ideal Body Weight Calculator
Calculate IBW and Adjusted Body Weight using multiple clinical formulas
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Please enter a valid height (e.g. 5 feet 10 inches).
About Ideal Body Weight Calculator
Ideal Body Weight (IBW) is a clinical estimate of a person's optimal weight based on their height and sex. It is widely used in medicine for calculating medication doses, ventilator settings, and nutritional requirements — not as a personal weight-loss goal.
This calculator implements four validated formulas: Devine (1974), the most commonly referenced in clinical practice; Hamwi (1964), originally developed for insulin dosing; Robinson (1983) and Miller (1983), which are later revisions with slightly different coefficients.
Adjusted Body Weight (AdjBW) is calculated when a patient's actual weight exceeds 130% of their IBW. The standard formula — IBW + 0.4 × (Actual − IBW) — is used for drug dosing in obese patients, as it accounts for the fact that adipose tissue is not entirely metabolically inert.
These calculations are clinical reference tools. They are not diagnostic and should not replace professional medical judgment.
How to Use the Ideal Body Weight Calculator
- 1 Select your unit system — Imperial (feet/lbs) or Metric (cm/kg).
- 2 Choose your biological sex — formulas use different base weights for males and females.
- 3 Enter your height. Results update automatically as you type.
- 4 Optionally enter your actual weight. If it exceeds 130% of IBW (Devine), the Adjusted Body Weight is shown.
- 5 Review the formula table for individual results and the equations used.
Frequently Asked Questions
Which IBW formula is most accurate?
No single formula is universally best. The Devine formula is most widely cited in clinical literature and used as the default for drug dosing and mechanical ventilation. Robinson and Miller formulas tend to give slightly lower values and were developed to address perceived overestimates in Devine. Use Devine when in doubt.
What is Adjusted Body Weight and when is it used?
Adjusted Body Weight (AdjBW) is used when a patient is more than 30% above their IBW. For hydrophilic drugs, using actual weight would overdose the patient, but using IBW alone would underdose. AdjBW corrects for this by factoring in a portion (40%) of the excess weight. It is commonly used for aminoglycosides, heparin, and nutritional support calculations.
Is IBW a good weight-loss goal?
IBW is a clinical reference, not a personal target. It does not account for body composition, muscle mass, age, or ethnicity. Many fit, healthy individuals fall outside IBW ranges. For personal health goals, consult a registered dietitian or physician.
Why are the formulas only valid above 5 feet?
All four formulas were derived from population data of adults at or above 5 feet (60 inches). Below that height, the linear extrapolation produces unreliable results. For shorter individuals, alternative methods are recommended.
Does IBW differ between males and females?
Yes. Each formula uses different base values for males and females, reflecting average differences in bone density and lean body mass. At the same height, males typically have a higher IBW estimate than females.
How does this compare to BMI?
BMI is a ratio (weight ÷ height²) with standard cut-offs for all individuals. IBW gives a specific target weight derived from a linear formula based on height and sex. In clinical settings, IBW is preferred for drug dosing, while BMI is used for population screening and diagnosis.