Ideal Body Weight Calculator

Ideal body weight (IBW) is a single number, derived from height and sex, that estimates the target weight most strongly associated with the lowest medical and metabolic risk for the average adult. The concept was born inside hospitals — specifically, inside the pharmacy. Many drugs are dosed by body weight, but their volume of distribution scales with lean mass, not adipose tissue, which means dosing a 200-pound bodybuilder and a 200-pound sedentary patient by total body weight gives wildly different blood-concentration profiles. Dr. Ben Devine solved that in 1974 by publishing the Devine formula: a simple linear equation that gives a single IBW for any height-and-sex pair. Almost every clinical pharmacy still uses it for drug dosing, ventilator settings, and creatinine clearance.

Devine was not the first attempt — Paul Broca published the height-minus-100 (men) / height-minus-104 (women) rule in Paris in 1871, George Hamwi formalized the dietitian-favorite version in 1964, and in 1983 two statistical updates appeared: Robinson trimmed the female numbers to fit modern adult cohorts, and Miller used linear regression on a larger sample to produce the highest target weights of the four classic formulas. The most recent academic addition is the BMI-22 method, which simply sets IBW at the midpoint of the healthy BMI range. It is the only formula that scales as height squared, which matters at the extremes of height where the linear formulas drift. We run all six in parallel so you see the spread, not a single number that pretends to be the truth.

When does each formula apply? Devine for medication dosing — full stop, this is the global clinical standard. Robinson and Miller as adult-population sanity checks. Hamwi when you are working with a registered dietitian who learned it in school. BMI-22 for modern fitness goal-setting because it scales smoothly with height. Broca as a back-of-envelope check, especially in Europe. Frame size — the small/medium/large adjustment — accounts for skeletal variation that height alone misses, and the standard 10% adjustment is the long-established way to handle it.

How to Use This Calculator (5-Step Guide)

1. 1. Pick Your Gender: IBW formulas have sex-specific constants because men and women carry different lean-to-fat ratios at the same height. Only BMI-22 is sex-neutral.
2. 2. Choose Your Frame Size: Use the elbow breadth test to identify small, medium, or large skeletal frame. Small subtracts 10%, large adds 10%.
3. 3. Enter Your Height: Toggle between feet-and-inches, inches alone, and centimeters — the calculator auto-converts the active value when you switch units.
4. 4. Enter Current Weight: Choose kg or lbs and type your current weight. The calculator outputs the gap between current weight and average IBW.
5. 5. Calculate, Compare, and Track: Hit Calculate for all six formulas, the IBW low/high range, the BMI 18.5-24.9 band, current-weight comparison, and bar chart.

Use Cases & Internal Tools

Pro Tips for Setting IBW Goals

• • Use the average, not a single formula: The mean of all six typically lands very close to BMI 22-23 — the lowest-mortality band in large epidemiology studies. Trust the consensus.
• • Adjust upward for muscle: All classic IBW formulas were built on lean cohorts. If you train 4+ times per week with visible musculature, add 4-8 kg to the formula average.
• • Use BMI-22 at the extremes: Under 5 ft 2 in or over 6 ft 4 in, the linear formulas drift. BMI-22 stays calibrated because it scales as height squared.
• • Frame size matters: Two adults at six feet can have a 6-7 kg gap in healthy target weight based on skeletal frame alone. The 10% adjustment is well-validated.
• • Re-measure rather than guess: Most adults overestimate height by half an inch. Measure barefoot once a year — IBW shifts about 1 kg per inch of true height.
• • For drug dosing, use Devine: No exceptions. Every other formula is for fitness, nutrition, or curiosity.
• • Treat IBW as a range, not a number: Daily weight swings of 1-2 kg are normal. Use the IBW range as your target band, not the average alone.

Whatever your context — clinical dosing, dietitian counseling, sport-specific cuts, or general health — the multi-formula approach is more informative than any single output. Bookmark this tool, run all six against your current height, and use the average plus frame adjustment as your target.