How wide is the healthy weight range really?

Wider than almost anyone expects. At 160cm it spans about 16kg, at 175cm about 20kg, and at 190cm about 23kg — because the range is a fixed BMI interval and BMI scales with height squared, so the window grows as people get taller. Every weight inside it produces the same result from the measure. The width is the most informative single number the calculation produces, and it is the one most calculators do not mention.

Is the middle of the range better than the edges?

No. This is a band within which BMI raises no flag, not a curve with an optimum. The thresholds at 18.5 and 25 are population conventions adopted in the 1990s, chosen as round boundaries for classifying groups rather than discovered in nature — and nothing changes about a body between a BMI of 24.9 and 25.1. Reading the centre as a destination imports a precision the underlying evidence never claimed.

Where did the "ideal weight" formulas come from?

Clinical estimation, not health research. Devine was published in 1974 in a pharmacy journal as part of work on dosing gentamicin, and became the standard drug-dosing reference. Hamwi was a bedside shortcut for dietitians in 1964. Robinson and Miller, both 1983, were revisions for drug dosage against updated insurance tables. None of them was validated as a statement about what anyone should weigh; the name stuck and the purpose was quietly forgotten.

Why do the four formulas give different answers?

Because each picks its own base weight and its own increment per inch, from different source data. Hamwi is the most generous and Miller the least; at 175cm they differ by about 3.3kg, and at short stature the gap can exceed ten. That scatter is the honest headline — if four published equations built for the same purpose cannot agree on your ideal weight to within several kilograms, the idea that there is a single correct figure is doing more work than the evidence supports.

Should the range be different for Asian populations?

The WHO issued supplementary cut-offs in 2004 saying so, putting overweight at a BMI of 23 rather than 25 and obesity at 27.5 rather than 30, because the standard thresholds understate metabolic risk in South and East Asian populations at the same BMI. At 175cm that lowers the top of the window from 76.3kg to about 70.1kg. The lower bound is unchanged. The four older formulas make no ethnic adjustment at all, having been derived largely from white American cohorts.

Does the range change with age?

The published thresholds do not, but the interpretation reasonably does. Body composition shifts with age — muscle is lost and fat tends to redistribute — so an older person can sit comfortably inside the range while having lost a good deal of lean tissue, and some research suggests a slightly higher BMI is associated with better outcomes in later life. None of that is reflected in a fixed 18.5 to 24.9 band, which is one of several reasons the range is a screening device rather than a description of anyone.

Does it apply to muscular people?

Poorly, and in a predictable direction. BMI is weight over height squared and cannot tell what the weight is made of, so someone carrying a lot of muscle reads high while being entirely healthy — which is why the measure misclassifies athletes routinely and why waist-based measures are often preferred for individuals. The range is a reasonable screen across a population and a blunt instrument for any particular person, most obviously this one.

What if my weight sits outside the range?

It is worth raising at a routine appointment, and it is not a verdict. The range is one of several screening measures and it sees only two numbers, so a reading outside it is a reason to look at things a calculator cannot — blood pressure, glucose, lipids, how you sleep and move, family history. What is worth avoiding is treating the nearest boundary as a target and acting on it alone. A doctor or a dietitian has context that no height-and-weight calculation can supply.

Why does this page not tell me how much to lose or gain?

Because a distance from a range stops being information and becomes a target, and a target is not something a calculator is in any position to set. The page will say which side of the range a weight sits on, which is the part that is genuinely useful for deciding whether to raise the question with someone. What happens after that depends on a great deal that two measurements cannot see, and it is properly a conversation with a doctor or a dietitian rather than a number printed on a screen.

Is BMI still worth using at all?

As a screen across populations, yes — it is cheap, consistent, and correlates well enough with outcomes at scale to remain the standard first pass. As a description of an individual it is weak, which is why guidance increasingly pairs it with a waist-based measure that says something about where weight sits. The honest position is that the range is a starting point that flags when a closer look might be worthwhile, and nothing beyond that.

Healthy Weight Range Calculator

A healthy weight is a range, and it is much wider than most people picture. At 175cm the window from a BMI of 18.5 to 24.9 runs from 56.7kg to 76.3kg — nearly twenty kilograms, every point of which carries exactly the same verdict. Nothing in the middle is better than the edges. It is a band within...

This is a range, and it is not a target. Every weight inside it carries the same verdict — nothing in the middle is better than the edges, and the window is far wider than most people assume. BMI also cannot see what a body is made of, so it misreads muscular and older bodies in opposite directions. This page will not tell you what to weigh, because no calculator is in a position to. If weight is something you find difficult to think about, or you have a history of disordered eating, a doctor or a dietitian is a far better place to take the question than any tool on the internet.

YOUR HEIGHT

Sex affects only the older "ideal weight" formulas further down. The healthy range itself is the same for everyone at a given height.

HEIGHT (CM)

WEIGHT (KG) — OPTIONAL

HEALTHY WEIGHT RANGE AT 175CM

56.7 – 76.3 kg

A window 19.6kg wide, from BMI 18.5 to 24.9. Every weight inside it carries the same verdict.

LOWER

56.7kg

UPPER

76.3kg

WINDOW

19.6kg

The window is 19.6kg wide, which is wider than people expect. That is the honest shape of the thing: a band rather than a point, with no reason to prefer the middle over either end. The four older formulas that offer a single "ideal weight" disagree with each other by 3.3kg at your height — all of them landing inside a window 6 times wider than their own disagreement. That is a good measure of how much precision the idea can actually carry.

The standard range is not the right one for everyone. In 2004 the WHO issued supplementary cut-offs for Asian populations, putting overweight at a BMI of 23 rather than 25, because the standard thresholds understate metabolic risk in those groups. At your height that lowers the top of the window from 76.3kg to 70.1kg — a difference of 6.1kg. If that applies to you, switch the cut-offs above.

Formula	Single figure	BMI it implies	Built for
Hamwi 1964	72.0 kg	23.5	a quick clinical estimate for dietitians
Devine 1974	70.5 kg	23.0	published for gentamicin dosing
Robinson 1983	68.9 kg	22.5	a revision for drug dosage
Miller 1983	68.7 kg	22.4	the least generous of the four

Where the single-number formulas actually came from. Devine was published in 1974 in a pharmacy journal, as part of work on dosing the antibiotic gentamicin. Hamwi was a bedside shortcut for dietitians a decade earlier. Robinson and Miller were revisions for drug dosage. None was validated as a statement about health, and none takes account of body composition, ethnicity or age. They persist as "ideal weight" because the name stuck, not because the research supports it.

What the range cannot see. BMI is weight over height squared and knows nothing else — not muscle, not bone, not where fat sits, not fitness, not blood pressure or glucose. A well-trained person often reads above the range while being entirely healthy, and an older person can read inside it while having lost a good deal of muscle. The boundaries themselves are population conventions adopted in the 1990s, not thresholds found in nature: nothing changes about a body between a BMI of 24.9 and 25.1.

THE RANGE

Nothing in the middle of this band is better than the edges. It is a range within which BMI raises no flag, not a distribution with a peak. Treating the centre as a goal reads a precision into it that the underlying evidence never had.

WHO BMI thresholds · live calculation

Created with❤️byeaglecalculator.com

HOW TO USE

1
Enter your height. That is all the range needs — the healthy window is a property of height, and it is the same for everyone at a given one.
2
Choose the cut-offs that apply. The standard WHO figures come largely from European data; the 2004 supplementary cut-offs for Asian populations put the top of the range meaningfully lower.
3
Add a weight only if you want to see where it sits. It is optional on purpose, and the page will tell you which side of the range you are on without calculating a distance from it.
4
Read the width of the window before anything else. It is the number that says most about how much the concept can actually tell you.

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Last updated: August 1, 2026 · WHO BMI thresholds, with the 2004 supplementary cut-offs for Asian populations · A range, not a target · Not medical advice.