“Ideal body weight” sounds like it should be a precise, personalized number, but it actually originated as a fairly narrow clinical tool: a formula developed in the 1970s to help estimate drug dosing for medications where dosing needs to scale with lean body size. It’s still used today, but understanding where it came from helps explain its real limitations.
Calculate Your Ideal Body Weight
Ideal Body Weight Calculator (Devine Formula)
The Devine formula was originally developed for medication dosing calculations, not as a target or ideal weight for individuals. It doesn’t account for muscle mass, frame size, or body composition.
Where This Formula Came From
The Devine formula was published in 1974, originally to help estimate a reasonable weight for calculating certain drug dosages (particularly for medications where dosing based on actual body weight, including fat mass, could be less accurate). It was never intended as a personal wellness or aesthetic target, though it later became popularized more broadly for that purpose.
Real Limitations to Keep in Mind
- It doesn’t account for muscle mass — a muscular, athletic person will often weigh well above their “ideal” number while being perfectly healthy
- It doesn’t account for frame size or bone density differences between individuals
- It was derived from a limited, older dataset, not a broad modern population sample
- It gives a single point number rather than a healthy range, which can create unrealistic expectations
What’s Generally More Useful
For most people, a combination of measures — BMI as a rough population screen, waist circumference or waist-to-height ratio for a sense of abdominal fat, and how your clothes fit or how you feel functionally — gives a more realistic picture than chasing a single “ideal weight” number derived from a decades-old dosing formula.
Frequently Asked Questions
Is ideal body weight still used clinically? Yes, it’s still used in some medical contexts (like certain medication dosing calculations), but it’s not intended as a personal weight-loss or fitness target for the general public.
Should I try to hit this exact number? Not necessarily — it’s a rough clinical estimate, not a personalized health goal. A healthcare provider can help set a more individualized and meaningful target if weight is a health concern.
Where “Ideal Body Weight” Formulas Actually Come From
Ideal body weight formulas, including the commonly used Devine formula, weren’t originally developed as a personal health target at all, they were created in the 1970s primarily to help clinicians calculate accurate medication dosing, since many drugs need to be dosed based on lean body mass rather than total weight, and total weight alone can be a misleading proxy in people with significant body fat variation. The Devine formula and similar equations (Robinson, Miller, Hamwi) estimate a population-average “ideal” weight based on height and sex alone, using data from life insurance actuarial tables and clinical populations, not from research on what body weight is actually optimal for long-term health across different individuals.
This origin is important context because these formulas have since been widely repurposed in fitness and wellness contexts as a personal weight target, a use they were never designed or validated for, which is a meaningful mismatch between the tool’s original clinical purpose and its popular application today.
Why a Single Number Can’t Capture Individual Health
Like BMI, these formulas use only height and sex, ignoring body composition, frame size, muscle mass, and fat distribution entirely, which means two people of identical height calculated to have the same “ideal” weight could have dramatically different actual health profiles depending on how that weight is composed. A muscular, athletic person will often weigh considerably more than their formula-calculated “ideal” weight while being in excellent health, while someone at their exact calculated ideal weight but with low muscle mass and high body fat percentage could have worse metabolic health despite hitting the “ideal” number precisely.
Different formulas also produce meaningfully different results for the same person, since each was derived from a different dataset and population, which itself is a useful signal that none should be treated as a precise, individually validated target rather than a rough historical estimate.
What’s More Useful in Practice
Rather than targeting a formula-derived number, more individualized measures give a considerably more accurate picture of health-relevant weight: body composition (the ratio of fat to muscle), waist circumference or waist-to-height ratio for fat distribution, and functional markers like blood pressure, blood sugar, and cholesterol, which reflect metabolic health directly rather than through a proxy formula from the 1970s. Where these ideal weight calculators remain genuinely useful today is in the clinical medication-dosing context they were built for, and even then, they’re generally used alongside actual body weight and other clinical factors, not as a standalone personal health goal.
Sources
- Devine BJ. Gentamicin therapy. Drug Intelligence & Clinical Pharmacy, 1974
- National Library of Medicine — Ideal Body Weight Overview
- MedlinePlus (U.S. National Library of Medicine)
Final Thoughts
“Ideal body weight” is a useful historical clinical tool with a specific, narrow original purpose — not a personal target to chase. A fuller picture of health comes from combining several measures, not fixating on any single number.
This article is for general educational purposes and is not a substitute for personalized medical advice.
About the Author
This article was written and reviewed by Drxty Editorial Team, focused on translating public health information into clear, practical guidance for everyday readers. If you spot an error or have a correction, please contact us.