How the ideal body weight calculator works
Each formula starts with a base weight at 5 feet and adds a fixed amount for every inch above that. The Devine formula (1974) is the most widely used in clinical pharmacology.
Robinson (1983): men 52 + 1.9 · women 49 + 1.7
Miller (1983): men 56.2 + 1.41 · women 53.1 + 1.36
Hamwi (1964): men 48 + 2.7 · women 45.5 + 2.2
Clinicians use IBW to dose drugs that distribute mainly in lean tissue, to estimate kidney function in obese patients and to set tidal volume on ventilators (6 to 8 mL per kg of predicted body weight). None of these formulas account for muscle mass or frame size.
Worked example
A man who is 5 ft 10 in is 10 inches over 5 feet. Devine gives 50 + 2.3 × 10 = 73.0 kg (161 lb), Robinson 71.0 kg, Miller 70.3 kg and Hamwi 75.0 kg. A woman of the same height has a Devine IBW of 68.5 kg (151 lb).
Frequently asked questions
What is the most accurate ideal weight formula?
None is accurate for individuals. Devine is the clinical standard because drug-dosing studies use it.
Why is my ideal body weight lower than I expected?
The formulas were built for dosing, not appearance, and ignore muscle. A muscular person can be healthy well above IBW.
Do these formulas work for people under 5 feet?
They extrapolate poorly. Clinicians often subtract 2.3 kg per inch below 5 feet with caution.
What is predicted body weight?
In ventilator settings it is the Devine formula, used to choose safe tidal volumes.
Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.