How this instrument works
Ordinary BMI calculators run one direction: enter weight and height, get a ratio out. This instrument runs the same formula backwards — enter a target BMI and a height, and it solves for the one weight that would produce that ratio, using target weight equals target BMI times height in metres squared. It is the identical equation behind any BMI calculator, algebra rearranged rather than reinvented.
Pick a target BMI of 25 — the conventional upper edge of the range the CDC calls healthy — at a height of 1.75 metres, and the answer comes back at about 76.56 kilograms: the exact weight where this height crosses from healthy into overweight territory by the standard bands. Change the target to 22, nearer the middle of the healthy range, and the same style of question at 1.65 metres instead points to roughly 59.90 kilograms.
A figure from this page is a marker on a scale, not a verdict on how a person should look or a promise of health at that exact number. BMI cannot separate muscle from fat, so the 'target weight' returned describes a ratio, not a body composition — someone carrying unusual muscle mass may reach a healthier state well above the figure this instrument returns, and someone with little muscle may need to sit below it. Treat the output as a reference point for a conversation with a clinician, not a fixed finish line.
- Enter Target BMI — 18.5 to 25 covers the range generally considered healthy; other values represent the other categories.
- Enter Height in centimetres, metres, inches or feet; the sum runs in metres underneath.
- Read Weight at target BMI in kilograms or pounds, depending on your unit choice.
- Recalculate with a different Target BMI to see how the same height maps to other category edges.
Worked example — target BMI 25 at 1.75 m
Square 1.75 metres: 1.75 × 1.75 = 3.0625 square metres. Multiply by the target BMI of 25: 25 × 3.0625 = 76.5625, which this instrument rounds to 76.56 kilograms — the weight at which 1.75 metres crosses the line from healthy into overweight.
Lower the target to 22 at a height of 1.65 metres: 1.65 squared is 2.7225, times 22 gives 59.895, rounding to 59.90 kilograms. Raise the target instead to 30 — the conventional obese threshold — at 1.80 metres: 1.80 squared is 3.24, times 30 comes to an exact 97.2 kilograms, useful as a line to stay under rather than a figure to reach.
Questions
How does this calculator work backwards from a normal BMI tool?
It rearranges the same formula. Ordinary BMI takes weight and height and produces a ratio; this page takes a target ratio and a height and solves for the one weight that satisfies it, using target weight equals target BMI times height in metres squared. No new science is involved — it is algebra, not a different model of the body.
What target BMI should I actually use?
That depends on where a person wants to sit inside, or at the edge of, the standard bands — 18.5 to 25 covers what the CDC labels healthy, so many people pick 24 or 25 as a target just inside that range. This instrument does not know your medical history, so treat any target chosen here as a starting point for a conversation with a clinician, not a self-contained prescription.
Why do two different heights give such different target weights for the same BMI?
Because height enters the formula squared, so a modest difference in height produces a larger difference in the matching weight. A target BMI of 22 at 1.65 metres points to about 59.90 kilograms, while the identical target of 22 at a taller height returns a noticeably larger figure — the squared term does most of the work.
Is the weight this page returns a healthy weight for me specifically?
Not necessarily — it is the weight that produces a chosen ratio, and BMI cannot see muscle, fat distribution, frame size, or medical history. Two people at an identical target weight and height can be in very different states of health. Use the figure as one reference point, alongside waist measurement and a clinician's assessment, rather than a stand-alone target.
Can I use this to set a weight-loss goal?
Yes, that is exactly what it is built for — pick a target BMI inside the healthy range, enter a height, and the resulting kilogram figure gives a concrete number to plan toward instead of an abstract ratio. Pair it with a realistic timeline and, ideally, guidance from a clinician or dietitian, since how that weight is reached matters as much as the number itself.
References
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.