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Geriatric BMI Calculator

Created by Joanna Michałowska, PhD and Aleksandra Zając, MD
Reviewed by Dominik Czernia, PhD and Jack Bowater
Based on research by
Jane E Winter, Robert J MacInnis, Naiyana Wattanapenpaiboon, Caryl A Nowson BMI and all-cause mortality in older adults: a meta-analysis; The American journal of clinical nutrition; April 2014See 1 more source
Kathryn N. Porter Starr, PhD, RD, and Connie W. Bales, PhD, RD Excessive Body Weight in Older Adults: Concerns and Recommendations; Clinics in Geriatric Medicine; Aug 2015
Last updated: Jan 18, 2024


This geriatric BMI calculator is a tool created for adults who are over 65 years of age. Based on your height and weight, it will calculate your BMI and determine if you are underweight, overweight, or a healthy weight. Read the article below to find out why BMI is not accurate for the elderly and what are the healthy ranges for BMI for seniors.

Are you under 65 years of age, meaning that the BMI calculator for the elderly is not suitable for you? Check our BMI calculators collection and find the one that is right for you:

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

Why is BMI not accurate for elderly?

Body mass index (BMI) is a value calculated from the weight and height of a person. A BMI over 25 is associated with higher all-cause mortality and an increased risk of suffering from various diseases, including cardiovascular disease and diabetes. Therefore, the normal ranges for BMI have been worked out to be between 18.5 and 25 kg/m².

Although BMI can be used on most adults, it does have some limitations:

  • It may overestimate body fat in athletes and people who have a muscular build; and
  • It may underestimate body fat in older persons and people who do not have a lot of muscle tissue.

Moreover, recent research showed that for older populations, being overweight is not associated with an increased risk of mortality. Therefore, different ranges for healthy BMI were found. Check the paragraphs below to find out more about BMI for seniors.

BMI for older adults — geriatric BMI guidelines

We hope that we answered the question, "Why is BMI not accurate for the elderly?", but who do we classify as "the elderly" in the first place? According to WHO, an older person is someone who is 65+ years old (sometimes 60+). Based on extensive research, different BMI categories were set for older adults, where healthy weight was defined as a BMI ranging from 23 to 29.9 kg/m². This stems from the fact that researchers noticed that a BMI below 23 and above 33 is associated with a significantly increased risk of mortality.

But why are geriatric BMI guidelines different from the general population? Human bodies change with age - an older person has more fatty tissue than a younger individual. Moreover, a higher BMI is associated with greater energy stores and a better nutritional state overall. This is really important when serious chronic health conditions (usually associated with age) are developed, e.g., chronic heart failure or cancer cachexia.

BMI chart for elderly

Below, we present a BMI chart for seniors together with a regular BMI chart.

BMI chart for seniors

BMI

Weight status

<23 kg/m²

Underweight

23-29.9 kg/m²

Normal weight

≥30 kg/m²

Overweight / Obese

BMI chart for the general population

BMI

Weight status

<18.5 kg/m²

Underweight

18.5-24.9 kg/m²

Normal weight

25-29.9 kg/m²

Overweight

≥30 kg/m²

Obese

Geriatric BMI calculator

How does the geriatric BMI calculator work?

  1. It calculates BMI from the regular equation shown below:

    BMI = weight [kg] / height² [m²]

    Don't worry about the units! Our geriatric BMI calculator has a built-in weight and length converter, so you can use either the metric or imperial system.

  2. Once BMI is calculated, a BMI category for the elderly is assigned.

Let's use a practical example to make sure that everything is clear. We will calculate BMI for 70-year-old Audrey, who is 162 cm tall and weighs 70 kilograms.

BMI = weight [kg] / height² [m²]

BMI = 70/ 1.62²

BMI = 70/ 2.6244

BMI = 26.7

Our BMI calculator for seniors displays the result according to categories for BMI for seniors: Audrey has a healthy weight.

FAQ

How do I calculate the geriatric BMI?

To calculate the geriatric BMI:

  1. Calculate the BMI normally, using the formula BMI = weight [kg] / height² [m²].
  2. Assign the person to a category that is different from the ones for the general population:
    • <23 kg/m² Underweight;
    • 23-29.9 kg/m² Normal weight; and
    • ≥30 kg/m² Overweight/Obese.
  3. That's it!

Is an elder person overweight if he is 1.75 m tall and weigh 65 kg?

No, the person is slightly underweight. To calculate this result, follow these instructions:

  1. Calculate the BMI of the person with the following formula:

    BMI = weight [kg] / height² [m²] = 65 kg/1.75² m² = 21.2 kg/m²

  2. Check the categories of BMI for elderly people: the underweight category contains BMI smaller than 23 kg/m².

You can infer that the person is slightly underweight.

Why is the geriatric BMI different?

The calculations and categories of the BMI for the general population don't fit the body structure of elderly people, where the muscular mass decreases, not necessarily leading to overweight. It's also been proved that elderly people have different tolerance for weight gain from younger ones. Therefore, a change in the categories of BMI was needed to provide a more suitable placement.

What is a good BMI for an 80 years old person?

A BMI between 23 kg/m² and 29 kg/m² is suggested for people over 65. This recommended value is noticeably different from the general population, where for younger people, normal weight corresponds to BMI between 18.5 kg/m² and 24.9 kg/m². The change reflects natural modifications in the body structure (reduced muscular mass, for example).

Joanna Michałowska, PhD and Aleksandra Zając, MD
Related calculators
Age
yrs
Weight
lb
Height
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BMI
Results interpretation:
BMIWeight status
<23Underweight
23-29.9Normal
>=30Overweight/obese
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