Healthy Weight Ranges by Height: How Ideal-Weight Formulas Work

"What should I weigh for my height?" is one of the most common questions people bring to a scale, and a whole family of ideal body weight (IBW) formulas exists to answer it. Plug in your height and sex, and formulas named after their creators (Devine, Robinson, Miller, Hamwi) return a single target weight in seconds. They're quick and easy, which is exactly why they persist. But these formulas were never designed to define personal health, and taking them literally can be misleading. Here's how they actually work and where to be careful.

Where Ideal-Weight Formulas Came From

Most of the ideal-weight formulas in common use were not created to help people diagnose their fitness. The best-known one, the Devine formula, was published in 1974 to help clinicians calculate medication doses. Many drugs are dosed by body weight, and for very tall or very short patients, actual weight can skew a dose, so Dr. Devine proposed a standardized "ideal" weight based only on height and sex.

The formula caught on far beyond pharmacy because it was simple and gave a clean single number. Later researchers, including Robinson, Miller, and Hamwi, published their own variations that adjust the baseline and the per-inch increment slightly. They all share the same basic shape: a fixed base weight at 5 feet (about 152 cm), plus a set amount added for every inch of height above that.

How the Devine and Robinson Formulas Compare

The two formulas you'll most often see in calculators are Devine and Robinson. Both start from 5 feet and add weight per additional inch, but they use different constants:

• Devine (1974) — Men: 50 kg + 2.3 kg per inch over 5 feet. Women: 45.5 kg + 2.3 kg per inch over 5 feet.
• Robinson (1983) — Men: 52 kg + 1.9 kg per inch over 5 feet. Women: 49 kg + 1.7 kg per inch over 5 feet.

Because the increments differ, the formulas can disagree by several pounds for the same person, especially at taller heights. That disagreement is a useful reminder: there is no single scientifically "correct" ideal weight. Each formula is a slightly different convention, and none of them is a law of nature.

What These Formulas Get Right, and What They Miss

Height-based formulas do capture something real: taller people generally have more lean body mass and larger frames, so a reasonable weight scales up with height. As a rough orientation point, that's helpful. But they share the same core blind spots, and then add a few of their own.

• They ignore body composition. Like BMI, ideal-weight formulas can't tell muscle from fat. A muscular person may sit "over" their formula weight while being lean and healthy.
• They assume one number, not a range. Healthy weight is genuinely a range, not a point. Two people of the same height and sex can both be healthy at noticeably different weights.
• They barely account for frame size. The classic formulas use only height and sex. Some older tables tried to adjust for small, medium, and large frames, but most calculators drop that nuance entirely.
• They were built on limited populations. These formulas were derived decades ago from narrow samples and don't reflect the full diversity of ancestry, age, and build. At the extremes of height, they can drift toward implausible values.
• They don't fit everyone. For pregnant people, children and teens, older adults with muscle loss, and athletes, a single height-based target simply doesn't apply.

A Healthy Weight Is a Range

This is why many clinicians prefer to express a healthy weight as a span rather than a single figure. One common approach is to take the healthy BMI range (18.5 to 24.9, per the CDC) and translate it into a weight range for your height. For someone 5 feet 8 inches tall, for example, that BMI range works out to roughly 122 to 164 pounds. That's a wide window, and that width is honest: it reflects the real variation in healthy bodies rather than pretending there's one perfect number.

How to Use an Ideal-Weight Number Wisely

Treat any single ideal-weight figure as a ballpark, not a bullseye. Here's how to keep it in perspective:

• Look at a range, not a point. If a formula says 160, read it as "somewhere in a healthy band around that," not "exactly 160 or you've failed."
• Cross-check with other measures. Pair it with your BMI, your waist circumference, and how your body actually performs and feels.
• Watch trends over time. The direction and stability of your weight usually matter more for health than hitting a specific formula-derived target.
• Consider your starting point. Research and major medical groups note that even a modest 5 to 10 percent change in body weight can meaningfully improve blood pressure, blood sugar, and cholesterol, often long before reaching any "ideal" number.

The Practical Takeaway

Ideal-weight formulas like Devine and Robinson are handy for a quick orientation, and they still do their original clinical job of standardizing medication dosing. But as personal health goals they're blunt instruments: they see only your height and sex, and they hand back a single number where biology offers a range. Use them for context, not as a scorecard, and don't let a formula's target override how your body is actually doing.

If you're trying to decide on a healthy weight goal, especially if you have a medical condition, are pregnant, are an older adult, or are an athlete, work with a doctor or a registered dietitian. They can set a target that fits your body composition, health history, and life stage, rather than a one-size-fits-all figure derived from height alone.