Growth & measurement
Ideal body weight calculator
Lungs are sized by height, not by weight — the Devine number is what tidal volumes and many drug doses should be counted against.
A 178 cm man about to be ventilated with lung-protective settings.
IBW 73.2 kg (Devine)
Tidal volumes of 6–8 mL/kg IBW give a target of roughly 440–585 mL — set from his height, regardless of whether he weighs 70 kg or 120 kg.
Who this is for
For clinicians setting up lung-protective ventilation — where 6–8 mL/kg tidal volumes are per kilogram of ideal, not actual, weight — and for prescribers dosing hydrophilic drugs or deriving adjusted body weight for renal-clearance estimates in obesity. Height and sex are all it asks; the Devine result follows immediately.
How it works
What it calculates
Ideal body weight by the Devine formula: 50 kg (male) or 45.5 kg (female) plus 2.3 kg per inch of height over 152 cm.
When to use it
Lung-protective ventilation (tidal volumes of 6–8 mL/kg are per kg of ideal, not actual, weight) and dosing of hydrophilic drugs.
Related calculations
Adjusted body weight — IBW plus 40% of the excess over IBW — is often used for drug dosing in obesity, including Cockcroft-Gault creatinine clearance.
Built on published evidence
- Devine: 50 kg (male) / 45.5 kg (female) + 2.3 kg per inch over 152 cm. Not defined below 152 cm. Reference: Devine 1974
Codification last reviewed 2026-08-28, and checked against published reference values in automated tests on every release — see the full evidence ledger.
Questions clinicians ask
Which formula does the calculator use?
Devine (1974): 50 kg for men or 45.5 kg for women, plus 2.3 kg per inch of height over 152 cm. It is not defined below 152 cm, and the tool says so rather than extrapolating.
Why is tidal volume based on ideal rather than actual weight?
Lung size scales with height and sex, not with body mass — ventilating an obese patient by actual weight delivers oversized breaths. Lung-protective ventilation targets 6–8 mL per kilogram of ideal body weight.
What about drug dosing in obesity?
Adjusted body weight — IBW plus 40% of the excess of actual over ideal — is often used for dosing in obesity, including Cockcroft-Gault creatinine clearance. The CrCl tool in the app pairs with this one for exactly that.
Does it work offline?
Yes — the whole app works offline once loaded, and nothing you enter is stored or transmitted; values stay in your browser tab only.
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