Ideal Body Weight Calculator
Estimates your ideal body weight using the Devine formula based on height and sex. Used by clinicians to guide medication dosing and assess healthy weight targets.
About this calculator
The Devine formula estimates ideal body weight (IBW) in kilograms based on height in inches and sex. For males: IBW = 50 + 2.3 × (height_in − 60). For females: IBW = 45.5 + 2.3 × (height_in − 60). Height in centimeters is first converted to inches by dividing by 2.54. The formula was originally developed in 1974 to guide drug dosing, particularly for medications that distribute poorly into fatty tissue. It assumes a reference frame where 5 feet (60 inches) is the baseline, adding 2.3 kg for every inch above that. IBW is not a fitness goal but a clinical benchmark used alongside actual body weight in pharmacology and respiratory care.
How to use
Suppose a female patient is 170 cm tall. First convert height: 170 ÷ 2.54 = 66.93 inches. Then apply the female Devine formula: IBW = 45.5 + 2.3 × (66.93 − 60) = 45.5 + 2.3 × 6.93 = 45.5 + 15.94 ≈ 61.4 kg. For a male of the same height: IBW = 50 + 2.3 × 6.93 = 50 + 15.94 ≈ 65.9 kg. Enter your height in cm and select your sex to get your result instantly.
Frequently asked questions
What is the Devine formula and why is it used for ideal body weight?
The Devine formula was introduced by Dr. B.J. Devine in 1974 primarily to standardize drug dosing. It provides a simple linear estimate of ideal body weight based on height and sex. Clinicians use it because many drugs — especially those with narrow therapeutic windows — should be dosed on lean mass rather than total body weight. It remains widely used in critical care, anesthesiology, and respiratory therapy despite newer alternatives.
How accurate is the ideal body weight calculator for everyday fitness goals?
The Devine formula was designed for clinical pharmacology, not personal fitness. It does not account for muscle mass, bone density, age, or ethnicity, so it can underestimate healthy weight for muscular individuals and overestimate it for others. For fitness purposes, metrics like BMI, body fat percentage, or waist-to-hip ratio may offer a more complete picture. Think of IBW as a clinical reference point rather than a personal weight-loss target.
When should ideal body weight be used instead of actual body weight for dosing?
Ideal body weight is preferred when dosing medications that do not distribute well into adipose (fat) tissue, such as aminoglycoside antibiotics or certain chemotherapy agents. Using actual body weight in obese patients for such drugs can lead to overdosing. However, for drugs that do distribute into fat, adjusted body weight or actual body weight may be more appropriate. Always defer to clinical guidelines and a pharmacist when making dosing decisions.