How this calculator works
The 2019 GLIM consensus and its 2025 update identify low BMI as one phenotypic criterion: below 20 under age 70, or below 22 at age 70 and above. The corresponding Asian thresholds are 18.5 and 20. The comparison is strict: a BMI exactly on the boundary does not meet this criterion. GLIM first requires risk screening, then at least one phenotypic and one etiologic criterion for diagnosis. This page evaluates BMI only, without diagnosing or grading malnutrition. Oedema, fluid overload, height loss, muscle loss and measurement difficulties can affect older-adult BMI. The result is an estimate for information only and is not medical advice.
Formula
BMI = weight in kg / height in metres². Low-BMI criterion = BMI < the selected age-specific GLIM boundary. Boundary weight = boundary BMI x height².
Worked example
A 75-year-old at 1.70 m and 60 kg has BMI 20.76, below the general boundary of 22. At the same height, BMI 22 corresponds to 63.58 kg. At age 69, BMI 21 does not meet the general low-BMI criterion of below 20.
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Frequently asked questions
Is BMI 22 to 27 a prescribed healthy range for everyone over 65?
This calculator does not make that claim. It applies the specific GLIM low-BMI criterion and does not invent a universal older-adult target range.
Can a person with a higher BMI be malnourished?
Yes. Weight loss, muscle loss, intake and disease burden matter. A BMI above this boundary does not exclude malnutrition.
Why is the result different at 70?
GLIM uses an age boundary at 70, including the 70th birthday in the older group. This is a screening convention, not a sudden biological change.