In older adults a slightly higher BMI appears protective: studies show the lowest mortality around BMI 24–31 after age 65, and weight loss is often a warning sign of illness or malnutrition. Muscle loss (sarcopenia) also means BMI can hide low muscle mass.
How to use the Geriatric BMI Calculator
- Age
- Weight
- Height
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter age, weight and height. If height is hard to measure because of curvature of the spine, use the bedridden height estimation calculator first. The result is compared with the cut-offs used by the Nutrition Screening Initiative and in geriatric practice.
Inputs explained
| Field | What to enter |
|---|---|
| Age | In years |
| Weight | Units: kg, lb, st, g |
| Height | Units: cm, in, m, ft, mm |
What each result means
- BMI = [Weight]÷([Height]÷100)^2
- Weight at BMI 23 = 23×([Height]÷100)^2
- Weight at BMI 29.9 = 29.9×([Height]÷100)^2
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
BMI = weight ÷ height²
Older adults: < 23 underweight · 23–29.9 healthy · ≥ 30 overweight or obese
Worked example
Inputs — Age: 75 years; Weight: 68 kg; Height: 165 cm.
Results — BMI = 25; Weight at BMI 23 = 62.6 kg; Weight at BMI 29.9 = 81.4 kg.
Key terms
- Sarcopenia
- Age-related loss of muscle mass and strength.
Frequently asked questions
Why is the healthy range different after 65?
Higher BMI is linked with better survival in older adults, possibly because reserves help during illness.
Is unintentional weight loss a concern?
Yes – losing more than 5% in 6–12 months should be discussed with a doctor.
What else should be checked?
Muscle strength, appetite and a nutrition screen such as MUST or MNA.