Your details
For adults (18+). Weight is optional — add it to also see your BMI and daily calories.
Why height matters more than age
A healthy weight is a function of how tall someone is, not how many birthdays they've had. Two adults the same age can have completely different healthy weights if their heights differ, and two adults the same height can be the same age or forty years apart and still share roughly the same healthy range. That's why this calculator asks for height and sex first — age only comes into the calorie and metabolic-rate estimates further down, where it genuinely changes the number.
How the numbers are calculated
- Healthy range — the weights at which your BMI would sit at 18.5 and at 24.9, the standard boundaries of the "healthy weight" band.
- Ideal weight — a single figure from the Devine formula, a reference equation from clinical medicine that has been used to guide medication dosing for decades.
- BMI — your current weight divided by height squared, shown only if you entered a current weight.
- BMR — calories your body burns at complete rest, from the Mifflin-St Jeor equation, the version most dietitians consider the most accurate in general use.
- Daily calories — your BMR multiplied by an activity factor, giving a rough calorie target for maintaining your current weight.
Common questions
Why does this need my height, not just my age?
A healthy weight depends on how tall you are, not how old you are. Two 30-year-olds of different heights have different healthy weights. Age matters only for the calorie and metabolic-rate estimates, not for the weight range itself.
Why adults only?
Under 18, healthy weight is judged against age-and-sex growth charts and percentiles, not a fixed adult formula. That is a different calculation that needs paediatric reference data, so this tool sticks to ages 18 and up where it can be accurate.
Where do the healthy range and ideal weight numbers come from?
The range comes from the standard BMI band of 18.5 to 24.9 applied to your height. The single ideal-weight figure uses the Devine formula, a long-standing reference formula from clinical medicine. Both are estimates, not a verdict on any individual body.
Is this medical advice?
No. It is a general reference calculation. Muscle mass, bone density, pregnancy and many health conditions all affect what a healthy weight looks like for a given person, so treat this as a starting point and talk to a doctor for anything personal.
Is my data saved anywhere?
No. Everything is calculated in your browser and nothing is sent anywhere or stored.