Senior BMI Calculator

Body mass index is weight in kilograms divided by height in meters squared. The arithmetic is the same for older adults. This calculator is presented for ages 60 and older, but the CDC adult category reference covers adults aged 20 and older.

BMI = weight (kg) / height (m)². For a 70-year-old weighing 61 kg at 170 cm, BMI = 61 / 1.70² = 21.1073 kg/m², displayed as 21.11. The category is determined from the unrounded value.

Enter current measured height and weight. Imperial inputs use total inches and pounds, converted with 0.0254 m/in and 0.45359237 kg/lb. Age must be a whole number of at least 60; height and weight must be finite and positive. Changing an input clears the previous result.

The CDC adult categories (March 19, 2024) apply regardless of adult age, sex or race:

• Underweight: BMI below 18.5.
• Healthy weight: BMI 18.5 to less than 25.
• Overweight: BMI 25 to less than 30.
• Obesity: BMI 30 or greater.

These are screening categories, not diagnoses or individual targets. The obesity threshold remains 30 at age 75 and older. Rounding a displayed BMI to a boundary does not change how the underlying value is classified.

NICE NG246, recommendation 1.9.13, originally marked 2022 and retained in the current 2026 guideline, advises caution at age 65 and older. Interpretation should consider medical conditions, functional capacity and the possible protective association of a slightly higher BMI. It does not define a universal senior ideal-weight band.

BMI alone cannot assess nutritional status. This calculator does not combine weight loss, mobility and chronic conditions into a risk score. A person may need assessment even when their BMI is in the healthy-weight category.

Unintentional weight change, reduced mobility and difficulty eating are reasons to discuss the situation with a healthcare professional. They should not be converted into a low, moderate or high nutritional-risk label without an appropriate validated assessment.

Clinical nutrition screening tools have their own questions, eligibility criteria and interpretation. This BMI calculation does not substitute for them.

BMI does not distinguish fat from muscle and cannot measure strength or walking ability. The same BMI can occur with different body composition and function.

Sarcopenia refers to a muscle condition requiring assessment beyond height and weight. Neither a healthy-weight category nor a high BMI rules out concerns about muscle or function. A professional can decide whether strength, physical performance or body-composition assessment is appropriate.

BMI changes when either weight or measured height changes. For example, 70 kg at 1.70 m gives 24.22; the same weight at 1.65 m gives 25.71. A higher BMI in that comparison does not establish that fat mass increased.

Keep the measurement date and method when comparing results. Discuss unintentional weight changes with a healthcare professional rather than choosing a weight-loss or weight-gain plan from the category alone. This tool cannot establish the cause of a change.

Bring recent measured weights, measurement dates and a description of whether the changes were intentional. Note changes in appetite, eating or swallowing difficulties and the effect of mobility on obtaining or preparing meals.

Discuss relevant medical conditions and medicines with the professional assessing you. Appropriate nutrition advice, supplements and weight goals depend on more information than BMI; this calculator does not prescribe them.

Does the calculator set a different threshold at age 75?

No. It uses the CDC adult screening categories throughout its age range and adds the NICE interpretation caution from age 65.

Does a healthy-weight result mean no assessment is needed?

No. BMI is one screening measure. Unintentional weight change, eating difficulties and reduced function still warrant discussion.

Does the result give an ideal weight?

No. A screening category does not establish an individual treatment goal, and the tool does not supply a senior target band.

Sources: CDC Adult BMI Categories (March 19, 2024; adults 20+) and NICE NG246, Identifying and assessing overweight, obesity and central adiposity (2026), recommendation 1.9.13 (2022; ages 65+).

Sources and methods checked: 2026-09-30.