Ideal weight calculator

These formulas were not designed for you

The Devine formula, the most widely used of the four, was published in 1974 as a way to calculate drug dosages. It was never validated as a measure of health or attractiveness, and Devine himself presented it without supporting data. Robinson, Miller and Hamwi are similar in origin: practical clinical heuristics that spread because they were convenient.

They persist in medicine because dosing certain drugs by total body weight is inaccurate for heavier patients, and an estimate based on height is a reasonable proxy for lean mass. That is a genuinely useful application. Using them as personal targets is a repurposing they were never built for.

What the spread tells you

For a 172 cm adult, the four formulas typically disagree by four to six kilograms. None of them is more correct than the others — they are different curve fits to different populations. When four accepted clinical formulas cannot agree within several kilograms, that is a strong signal that a single ideal weight does not exist.

The healthy BMI range, shown alongside, spans about 19 kg for the same height. That width is not imprecision; it reflects the fact that people of the same height have genuinely different healthy weights depending on build, muscle mass and bone density.

Composition matters more than the number

Two people at the same height and weight can have very different health profiles. Muscle is denser than fat, so someone who lifts regularly may sit above the BMI range while carrying less fat than someone in the middle of it. This is why clinicians increasingly look at waist circumference, waist-to-height ratio and blood markers rather than weight alone.

The single most useful number here, if you want one, is waist-to-height ratio: keeping your waist under half your height is a simple, well-supported guideline that works across heights and does not require any formula.

Where these formulas do not apply

• Children and adolescents — growth charts and BMI percentiles are used instead, and adult formulas are meaningless.
• Pregnancy — weight gain guidance is entirely different and comes from a midwife or doctor.
• Older adults — a slightly higher BMI is associated with better outcomes in later life, and being underweight carries more risk than being modestly overweight.
• Athletes — lean mass puts many of them outside the range with no health implication whatsoever.
• Amputees and people with limb differences — height-based formulas need clinical adjustment.

If a weight target matters for a medical reason, that conversation belongs with a doctor or a registered dietitian who can look at the whole picture. If you find yourself checking numbers like these frequently or feeling distressed by them, that is worth mentioning to a GP too — it is a common experience and there is straightforward help available.

Common questions