Ideal Weight Calculator

Four old formulas, one honest range

"Ideal body weight" formulas are older than most people expect, and were built for narrower purposes than the phrase suggests. Devine's formula, from 1974, was designed to help estimate medication dosing in clinical practice — not to give members of the public a weight-loss target. Hamwi's rule, from 1964, comes from a similar clinical tradition, originally used in diabetes care. Robinson (1983) and Miller (1983) refined the same basic height-based structure with different constants. All four take the same simple shape — a base weight plus an amount per inch of height over five feet — and disagree with each other by a meaningful margin, which is exactly why this page shows all four as a range instead of presenting any one as correct.

Why they disagree

Each formula was fitted to a different reference population, at a different point in the twentieth century, for a different clinical use. None was built from a modern, general population sample the way Mifflin-St Jeor was for BMR. That's not a flaw specific to one of them — it's the nature of older, simple, height-only equations. They tend to agree reasonably well for average heights and diverge more at the tall and short ends of the range.

Why there's no single "ideal" number

None of these formulas knows your frame size, muscle mass, or training history — they take height and sex and nothing else. Two people of identical height can have very different amounts of muscle and bone density, and both can be perfectly healthy at meaningfully different weights. Treating any single output as a personal target overstates what a decades-old, two-variable equation can actually tell you.

How to use this range sensibly

Treat the span between the lowest and highest of the four figures as a loose historical reference, not a finish line. If your current weight already falls inside it, that's a reasonable, if crude, signal that your weight sits within a commonly cited range for your height — nothing more specific than that. If it falls outside the range, that alone isn't a verdict either way: someone with substantial muscle mass will reasonably sit above it, and it says nothing about body composition, fitness, or how you actually feel. For an actual working target, the full calorie calculator's target-weight field, paired with a goal and a realistic rate, gives you something to plan toward rather than just compare against.

Who this suits

Anyone curious about where these often-cited formulas come from and what they actually say, especially if you've seen one of them quoted elsewhere as if it were a precise, individual prescription. It's a reference point, not a plan.

Limitations

These are among the oldest and simplest formulas on this site, and they show it — no body composition, frame size, or goal is considered anywhere in the maths. If you want a number to actually work toward, the full calorie calculator's goal and target-weight tools, built on your calorie balance rather than height alone, are a better starting point.

Waist-to-Hip Ratio vs. BMI: Which to Trust? — another angle on "healthy weight" that isn't a single height-based number.
How to Actually Plan for Weight Maintenance — once you have a working range, how to actually hold a weight steady inside it.

Frequently asked questions

Where do these formulas actually come from?

Devine's formula (1974) was created to help estimate drug dosing in clinical medicine, not as general public health guidance — a detail often lost when it's repurposed as a fitness number. Robinson (1983) and Miller (1983) are later adjustments to the same basic idea, and Hamwi (1964) is an older, similarly-structured rule of thumb originally used in diabetes management. None were designed to hand someone a personal weight-loss target.

Why do the four formulas give different answers?

Each was fitted to a different reference population, at a different time, for a different clinical purpose. They agree reasonably well in the middle of the height range and diverge more at the extremes. That spread is exactly why this calculator shows a range across all four rather than picking one as authoritative.

Is there really a single "ideal" weight?

No — that framing oversells what any formula can know about an individual. Healthy weight depends on frame size, muscle mass, age, and factors no height-only equation captures. Treat the range here as a rough historical reference point, not a personal prescription.

How is this different from the BMI healthy weight range?

BMI's healthy range is derived mathematically from the 18.5–24.9 BMI band at your height. These four formulas are separate, older, height-based rules with their own independent histories and constants — they weren't built from BMI at all, which is part of why the two ranges don't line up exactly.

Should I try to reach the middle of this range?

Not necessarily. These formulas don't know your muscle mass, frame, or goals. They're offered here as historical context for a commonly asked question, not as a target — the full calorie calculator's goal and macro tools are a better fit for actually planning toward a weight.