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About this tool
BMI for adults over 65 with the age-adjusted 24-29 desirable range, knee-height stature estimation and a MUST malnutrition score.
This calculator gives BMI as weight in kilograms divided by height in metres squared, then reads it against the 24 to 29 desirable range that Lipschitz proposed for adults over 65 rather than the 18.5 to 24.9 band used for younger adults. It also estimates standing height from knee height using the Chumlea equations, for people whose spine has compressed or who cannot stand for a measurement, and scores malnutrition risk with the BAPEN MUST screening tool. In later life the bigger danger is usually being too thin, so the output leads with how far the weight sits below the desirable range.
Open Elderly BMI Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Uses the 24 to 29 desirable BMI band for 65+ instead of the general adult band.
Chumlea knee-height equations give a stature estimate for bed-bound or stooped patients.
Combines BMI, unplanned weight loss and acute illness into the 0, 1, 2+ risk categories.
Roughly 24 to 29, higher than the 18.5 to 24.9 band used for younger adults. A 2014 meta-analysis in the American Journal of Clinical Nutrition found the lowest all-cause mortality in adults 65 and over clustered near BMI 27.5, with risk rising below about 23.
BMI itself is the same formula at every age, but the risk attached to a given value shifts. Older adults lose muscle and bone, so a low BMI more often reflects frailty and malnutrition than leanness, and a modest fat reserve provides a buffer during illness and hospital stays.
Use the Chumlea knee-height equations. With the knee and ankle at 90 degrees, measure from the sole of the foot to the top of the thigh, then apply height = 64.19 − (0.04 × age) + (2.02 × knee height) for men and 84.88 − (0.24 × age) + (1.83 × knee height) for women, all in centimetres.
More than 5 per cent of body weight lost unintentionally over three to six months, and more than 10 per cent is scored as high risk by MUST. For a 60 kg person that is 3 kg and 6 kg respectively. Any unplanned loss at that scale is worth raising with a GP, because it often precedes a fall or a hospital admission.
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