Ideal weight calculator
There is no single official ideal weight figure, so this calculator uses the NHS healthy weight guideline, a BMI of 18.5 to 24.9, and converts that band into a weight range for the entered height, in metric or imperial. A Devine-formula figure is also shown for historical context. Individual needs vary, and this is general information, not medical advice.
How is the healthy weight range calculated?
The range comes from the NHS definition of a healthy weight, which is a BMI of 18.5 to 24.9.
BMI is weight in kilograms divided by height in metres squared, so rearranging that formula gives a weight for any BMI at a fixed height.
The tool multiplies height in metres squared by 18.5 for the lower figure and by 24.9 for the upper figure, following the NHS BMI band.
Anything between those two weights sits inside the NHS healthy band.
The Devine figure shown alongside comes from a separate, older method that is not an NHS guideline.
It starts from a base weight, 45.5 kg for women and 50 kg for men, and adds 2.3 kg for every inch of height above 5 feet.
It was built in the 1970s to help calculate medicine doses, not to judge general health, so it is included only for historical context.
| Figure | Basis |
|---|---|
| Lower healthy weight | Height squared times 18.5 (NHS BMI band) |
| Upper healthy weight | Height squared times 24.9 (NHS BMI band) |
| Devine formula (context only) | 45.5 kg (women) or 50 kg (men), plus 2.3 kg per inch over 5 ft |
This is general information rather than medical advice, and a doctor should be consulted about personal weight or health.
What would the range be for an example height?
Take a height of 170 cm, which is 1.7 metres.
Squared, that is 2.89.
Multiplying by 18.5 gives 53 kg and by 24.9 gives 72 kg, so the NHS healthy range is about 8 st 6 lb to 11 st 5 lb.
The Devine formula for a woman of this height returns 61 kg, shown only as historical context rather than NHS guidance.
Common questions
How is the healthy weight range calculated?
This calculator has no single official UK ideal-weight formula to follow, so it uses the NHS definition of a healthy weight, a BMI of 18.5 to 24.9, and applies those two values to the entered height. BMI is weight in kilograms divided by height in metres squared, so rearranging that formula for a fixed height gives a weight for each BMI value. The Devine formula shown alongside is a separate historical method, included only for context, and individual needs vary.
What would the range be for an example height?
Take a height of 170 cm, which is 1.7 metres. Squared, that is 2.89. Multiplying by 18.5 gives 53 kg and multiplying by 24.9 gives 72 kg, so the NHS healthy range is about 8 st 6 lb to 11 st 5 lb. The Devine formula for this example returns 61 kg, shown only as historical context.
What is the ideal weight for my height?
There is no single ideal weight, but the NHS defines a healthy weight as a BMI between 18.5 and 24.9, so there is a range rather than a single figure. This tool applies those two BMI values to the entered height to give the lower and upper healthy weight, in kilograms and stones. Individual needs vary and this is general information, not medical advice.
Why is it a range and not one number?
People of the same height carry different amounts of muscle and build, so the NHS healthy weight guidance spans a band rather than a single figure. Anywhere inside the 18.5 to 24.9 BMI range counts as healthy under that guidance. Sitting in the middle is not more correct than sitting near either edge.
What is the Devine formula?
The Devine formula is an older method from 1974 that estimates a weight from height and sex, starting from a base figure and adding 2.3 kg for each inch over 5 feet. It was designed for medicine dosing, not general health, and it is not an NHS guideline, so it is shown here only as historical context.
Does this work for everyone?
No. BMI is a rough guide for adults and does not suit very muscular people, pregnant women, or children, who use different growth charts. It also does not account for where fat sits. The range shown is general information, and a GP can give a fuller picture for personal circumstances.
What if I am outside the healthy range?
Being under or over the range slightly is common and this tool does not treat that as a diagnosis. Larger gaps are best discussed with a GP, who can look at waist measurement, activity and health history rather than weight alone. This calculator gives no recommendation on whether to change weight.
Sources & Rate Verification
Rates verified against official statutory guidance on 6 September 2026.