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Frailty Index Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Dominika Śmiałek, MD, PhD candidate and Rijk de Wet
Based on research by
Mitnitski AB, Mogilner AJ, Rockwood K. Accumulation of deficits as a proxy measure of aging.; Scientific World Journal; August 2001See 2 more sources
Mitnitski A, Collerton J, Martin-Ruiz C, Jagger C, von Zglinicki T, Rockwood K, Kirkwood TB. Age-related frailty and its association with biological markers of ageing.; BMC Medicine; July 2015Searle SD, Mitnitski A, Gahbauer EA, Gill TM, Rockwood K. A standard procedure for creating a frailty index.; BMC Geriatrics; September 2008
Last updated: Feb 28, 2024

The frailty index calculator offers you a comprehensive review of frailty assessment methods and allows you to compute the exemplary frailty score using the frailty index (FI). Keep reading and you'll learn about the frailty index, how it can be modified to fit a facility's needs, and it differs from the Rockwood frailty score. 📚

What is frailty index?

The frailty index (abbreviated FI) is a simple yet effective tool to assess frailty — a state of increased vulnerability to external stressors.

The frailty index consists of 30–40 variables that measure the patient's health deficits. The heart of the index is a ratio that compares present deficits to possible deficits. This intuitive definition can be expressed as a formula:

FI = Deficits present / Deficits measured

The FI will always evaluate to a number between 0 and 1, and can be expressed as a percentage. As with any index, higher numbers mean a higher intensity — frailty increases with the index.

Interestingly, we can fully modify the FI variables according to a given facility's needs. The specific creation guidelines guarantee the reproducibility of the findings.

Frailty assessment — other methods

We may assess frailty by the accumulation of deficits measured with the frailty index that our frailty score calculator computes for you. However, there's also a graphical method to assess frailty that was developed by Rockwood et al. and the Canadian Study on Health & Aging. This easy technique is based on 9 descriptions combined with simple images representing different stages of frailty accumulation. The simplicity of this solution allows for the quick & reliable evaluation of geriatric patients.

  • The Rockwood's frailty scale

Another study, this time by Fried et al., presents five criteria that make up a distinctive phenotype (a description of the patient's traits). These traits comprise of weight loss, exhaustion, low physical activity, slowness, and weakness.

  • The five Fried frailty criteria

Plenty of tests allow us to evaluate different aspects of older patients' lives; here are just a few:

How to create the frailty index?

The variables included in the frailty index questionnaire must follow a distinctive set of criteria:

  1. The frailty index should consist of at least 30–40 variables.
  2. Each deficit should be assessed to a number between 0 and 1.
  3. The listed deficits must be directly connected to the patient's health status.
  4. Each deficit's prevalence must increase with age.
  5. The chosen deficit must not be highly widespread in the population. A deficit that is saturated (i.e., too many people suffer from the condition) will result in a prevalence close to 100% in most cases and won't be an accurate measure of frailty.
  6. The set of chosen variables must measure the fitness of multiple systems. We cannot limit them to only brain functions, for example.
  7. We need to use precisely the same set of variables in a given series of measurements — this rule doesn't apply if we'd like to compare entire groups of data created with different indexes.

For more details, visit this article by Searle et al.

How to use the frailty index calculator?

Our frailty score calculator offers two options:

  1. The simple frailty index calculator computes the ratio between present and possible health deficits.
  2. The complete questionnaire combined with ready-to-go FI calculations offers all the steps needed for frailty assessment.

Let's focus on the second option:

  • To fully profit from the tool, fill in all the variables of the questionnaire.
  • Most questions require simple "Yes" or "No" answers.
  • You still need to input values for weight, height and grip strength.
  • The BMI for seniors will be calculated automatically.


How do you calculate the frailty index?

Calculation of the frailty index is the easiest part of the entire process:

Frailty index = Present deficits / Measured deficits

We might describe the frailty index as a ratio of health deficits present in a given patient vs. the total number of deficits considered in a given study. If our patient suffers from 5 out of 40 measured deficits, we may say that his frailty index equals FI = 5/40 = 0.125.

How do you assess frailty?

There are three popular ways to assess frailty:

  1. The Frailty Index, which consists of 30–40 variables, and each criterium can be rated from 0 to 1.

  2. The Clinical Frailty Score is a set of 9 descriptions accompanied by simple graphical illustrations.

  3. The Five Fried Frailty Criteria presents the phenotype of 5 traits in the patient: these are weight loss, exhaustion, low physical activity, slowness, and weakness.

How do you use the clinical frailty score?

The Clinical Frailty Score consists of 9 steps accompanied by simple images. It is recommended to use in people over 65 years without any long-term disability.

  • Any trained healthcare professional can perform the assessment — ask the patient's relative/carer/family about their well-being and capabilities two weeks before.

  • Time of assessment: <1 min.

  • Do not perform the evaluation based on the patient's current state.

  • Always check the score before the decision-making.

Łucja Zaborowska, MD, PhD candidate
Show sample questionnaire? (40×Q)
Health deficits present
Health deficits measured
Frailty index (FI)
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