BodyCalThe adult healthy range doesn't change with age
For all adults aged 20 and over, the World Health Organization defines a healthy BMI as 18.5 to 24.9, regardless of whether you're 25 or 75. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is classed as obese. There is no separate official BMI chart 'for your age' in adulthood.
Children and teenagers are the exception — their BMI is read against age-and-sex percentile charts, because growing bodies change rapidly. This article is about adults.
Why age still changes the interpretation
Even though the cutoffs stay fixed, what they mean for your health shifts with age. After about 65, several large studies suggest that being at the lower end of 'healthy' — or even slightly into the 'overweight' band — is associated with better outcomes, partly because a little reserve helps during illness and protects against frailty.
Body composition also drifts with age: people tend to lose muscle and gain fat even at a stable weight, so an older adult with a 'healthy' BMI can still carry more body fat than the number suggests. That's why BMI is a screening tool, not a diagnosis.
What to check alongside BMI
Waist circumference is the single most useful companion measurement. Carrying fat around the abdomen is more metabolically harmful than the same weight on hips and thighs, and a high waist measurement raises risk even when BMI looks fine.
If you're very muscular, BMI will overstate your risk, since it can't tell muscle from fat. In that case body-fat percentage or simply how your clothes fit tells you more than the scale.
Check your number and your healthy range
Our BMI calculator shows where you fall on a clear visual scale and gives the exact healthy weight range for your height. Use it as a starting point for a conversation, track it a few times a year rather than daily, and read it alongside your waist measurement and how you actually feel.