How this instrument works
The Frailty Index (FI) is a deficit-accumulation measure of accumulated health deficits in older adults, following the procedure Rockwood and Mitnitski's group described for building a standardized 30-to-40-item index. This calculator is a geriatric/clinical assessment instrument for researchers, clinicians, and geriatric-care contexts assessing how much accumulated health deficit a person carries — comparable in scope and stakes to this site's own APACHE II and SAPS II critical-care calculators. It is not a casual self-test, not a diagnostic tool on its own, and not a rule for making an individual treatment decision; a higher FI tracks with worse health outcomes across large study populations, but any one person's situation still depends on clinical judgment and context the index cannot capture.
The index sums 40 individually scored items — 14 activities-of-daily-living and instrumental-activities-of-daily-living (ADL/IADL) help-needed questions, 6 general-health and mood-adjacent items, 5 mood items, 8 common comorbidities, 1 cognitive test (the Mini-Mental State Exam, MMSE), and 6 physical-performance measures including body mass index — and divides the total by 40. Each item scores 0 (deficit absent), 1 (deficit fully present), or a fraction such as 0.25, 0.5, or 0.75 for a partial or graded response, so the running total can land anywhere from 0 to 40 in quarter-point steps. On sourcing: Searle et al.'s 2008 BMC Geriatrics paper is the primary methodology reference for this kind of index, and it both describes the general procedure for selecting frailty-index items and publishes a specific 40-item table (its Table 1 and Table 2) built by applying that procedure to its own study cohort. The 40-item enumeration and cutoffs used on this page follow that published table directly — see the references and the FAQ below for the one place where this page's wording departs from the source's own label.
Two sourcing details on this page are worth spelling out plainly. First, the item asking whether someone walks outside fewer than 3 days a week (walkOutsideLow) is scored as a full deficit point when the answer is Yes; this '<3 days/week' threshold is taken directly from the 'Walk outside' row of Table 1 in Searle et al. 2008, which lists exactly that cutoff — it reproduces the published table rather than representing a judgment call by this project. Second, each of the 8 comorbidity items (highBp, heartAttack, chf, stroke, cancer, diabetes, arthritis, lungDisease) offers three choices — No, 'Possible or unconfirmed diagnosis,' or Yes — scoring 0, 0.5, and 1 respectively. The primary source's own Table 1 codes these as 'Yes = 1, Suspect = 0.5, No = 0,' with no further elaboration of what 'Suspect' should mean in practice. This calculator relabels that middle option as 'Possible or unconfirmed diagnosis' as an honest, plain-language equivalent of the source's own undefined term — a genuine wording choice on this project's part, even though the underlying 0/0.5/1 scoring is taken straight from the table.
Body mass index plays two roles at once, which is easy to miss on first read. bmi (computed from height and weight) is itself one of the 40 scored items — bmiDeficit scores 1 point when bmi is under 18.5 or 30 and over, 0.5 when bmi sits in the overweight 25-to-29.9 band, and 0 in the mid-range — and that same bmi value also selects which cutoff band applies to the grip-strength item (gripDeficit), which uses a nested table with 4 BMI bands for women and 3 for men, adapted from the sex- and body-size-adjusted cutoffs used in the Fried/Cardiovascular Health Study frailty-phenotype literature. Peak flow (peakFlowDeficit) and shoulder strength (shoulderDeficit) are simpler: each uses one cutoff for women and a different single cutoff for men, with no BMI dependency. The MMSE cognitive item (mmseDeficit) is graded across five tiers rather than a single yes/no cutoff — reflecting that cognitive impairment sits on a spectrum rather than a binary state.
- Answer the 14 daily-activity items — bathing, dressing, chair, walkHouse, eating, grooming, toilet, stairs, lift10, shopping, housework, mealPrep, medication, finances — Yes only where help is actually needed.
- Answer the 6 general-health items: lostWeight, selfRated, healthWorse, bedHalfDay, cutActivity, and walkOutsideLow (see the FAQ for its source).
- Answer the 5 mood items — effort, depressed, happy, lonely, goingTrouble — each as Rarely, Some of the time, or Most of the time.
- Answer the 8 comorbidity items — highBp, heartAttack, chf, stroke, cancer, diabetes, arthritis, lungDisease — as No, Possible or unconfirmed diagnosis, or Yes.
- Enter mmse (0-30), sex (female), height and weight (which compute bmi), peakFlow, shoulder and grip strength, and usualPaceSec/rapidPaceSec walk times.
- Review bmi, the adlSum, moodSum, and comorbidSum subtotals, and the final deficitsPresent (of 40) and frailtyIndex (0-1) at the bottom.
Worked example: a moderate-deficit case, 17.00 of 40
Among the 14 ADL/IADL items, only chair (getting in/out of a chair), stairs, lift10, shopping, and housework are marked Yes, each worth 1 point, for an adlSum of 5. Of the 6 general-health items: lostWeight is No (0), selfRated is Good (0.5 on the Excellent/Very good/Good/Fair/Poor scale), healthWorse is Yes (1), bedHalfDay is No (0), cutActivity is Yes (1), and walkOutsideLow is Yes, scoring a walkOutsideDeficit of 1. That subtotal so far: 5 + 0 + 0.5 + 1 + 0 + 1 + 1 = 8.5.
Of the 5 mood items, effort, depressed, and goingTrouble are each 'Some of the time' (0.5 apiece), happy is also 'Some of the time' (0.5 on its own reversed scale), and lonely is 'Rarely' (0), for a moodSum of 2.0. Of the 8 comorbidities, highBp, diabetes, and arthritis are each Yes (1 point each) and the remaining five are No, for a comorbidSum of 3. The mmse score is 26, which is 24 or above, so mmseDeficit is 0 — no cognitive deficit scored. Running total: 8.5 + 2.0 + 3 + 0 = 13.5.
Height 1.60 m and weight 72 kg give a bmi of 28.125 (28.1), landing in the 25-to-29.9 overweight band, so bmiDeficit scores 0.5. That same bmi also picks the grip-strength band: for a woman with bmi between 26 and 29, the cutoff is grip ≤ 18 kg, and this case's grip of 15 kg falls under it, so gripDeficit scores 1. peakFlow of 280 L/min is at or below the female cutoff of 310, so peakFlowDeficit is 1; shoulder strength of 8 kg is at or below the female cutoff of 9, so shoulderDeficit is 1. usualPaceSec of 14 seconds and rapidPaceSec of 9 seconds both fall under their respective 16-second and 10-second thresholds, so usualPaceDeficit and rapidPaceDeficit are both 0.
Adding the physical-performance and BMI items to the running total: 13.5 + 0.5 (bmiDeficit) + 1 (peakFlowDeficit) + 1 (shoulderDeficit) + 1 (gripDeficit) + 0 (usualPaceDeficit) + 0 (rapidPaceDeficit) = 17.0. deficitsPresent is 17.00 of 40, and frailtyIndex = 17.00 ÷ 40 = 0.425 — a score commonly described as landing in the 'vulnerable' or 'pre-frail' range, well above the fit range and below the frail range described in the FAQs.
Questions
What is the Frailty Index used for?
The Frailty Index counts how many of 40 defined health deficits a person has and expresses that count as a 0-to-1 fraction, following the deficit-accumulation approach Rockwood and Mitnitski's group formalized. It is built for researchers, clinicians, and geriatric-care contexts — for risk stratification, tracking accumulated deficit over time, and informing care-planning discussions — not for a casual self-test, a standalone diagnosis, or a rule for making an individual treatment decision. A higher FI tracks with worse outcomes across study populations, but any one person's course still depends on clinical judgment and factors the index alone cannot capture.
What does the 0-to-1 Frailty Index score actually mean?
The score is simply deficitsPresent divided by 40 — the fraction of assessed items scored as a deficit. The frailty literature commonly cites rough interpretation bands: below 0.10 as relatively fit or non-frail, 0.10 to 0.25 as vulnerable or pre-frail, and above 0.25 as frail. These are widely used, commonly-cited bands rather than one single universal cutoff adopted by every study, and, like this site's APACHE II and SAPS II score-interpretation FAQs, they should sit alongside clinical judgment and the full picture, not stand alone as a diagnosis.
Why does 'walks outside fewer than 3 days a week' use that specific cutoff?
This item (walkOutsideLow) scores a full deficit point when someone walks outside fewer than 3 days a week. That threshold is not a project judgment call — it is taken directly from the 'Walk outside' row of Table 1 in Searle et al. 2008 (BMC Geriatrics), which lists the cut point as '<3 days = 1' for this item, meaning fewer than 3 days a week scores the full deficit point and 3 or more days scores none. This page reproduces that published cutoff rather than interpreting an ambiguous source.
What does 'Possible or unconfirmed diagnosis' mean for the comorbidity items?
Each of the 8 comorbidity items (highBp, heartAttack, chf, stroke, cancer, diabetes, arthritis, lungDisease) offers three choices scoring 0, 0.5, or 1: No, 'Possible or unconfirmed diagnosis,' and Yes. Table 1 of the primary source, Searle et al. 2008, codes each item only as 'Yes = 1, Suspect = 0.5, No = 0,' with no further elaboration anywhere in the paper of what should count as 'Suspect.' This calculator relabels that middle option as 'Possible or unconfirmed diagnosis,' a plain-language stand-in for the source's undefined term — the 0/0.5/1 scoring is taken straight from the table; only the wording of the middle label is this project's own interpretation.
Why does BMI count as both a scored deficit and a cutoff for grip strength?
bmi (weight in kg divided by height in m squared) is itself one of the 40 scored items: bmiDeficit scores 1 when bmi is under 18.5 or 30 or above, 0.5 in the 25-to-29.9 overweight band, and 0 in between. That same bmi value is then reused to pick which cutoff applies to the grip-strength item (gripDeficit), which uses a nested table of 4 BMI bands for women and 3 for men — so one bmi calculation feeds two separate parts of the score. This dual role is a genuinely non-obvious feature of the instrument: changing height or weight can shift both the bmiDeficit score directly and which grip-strength band applies.
Why is the grip-strength cutoff more complicated than peak flow or shoulder strength?
gripDeficit uses a nested table: which grip-strength cutoff applies depends on both sex and the person's BMI band — 4 BMI bands for women, 3 for men — because grip-strength norms vary meaningfully by both sex and body size, an approach adapted from the sex- and size-adjusted cutoffs used in the Fried/Cardiovascular Health Study frailty-phenotype literature. peakFlowDeficit and shoulderDeficit are simpler by comparison: each uses just one fixed cutoff for women and a different fixed cutoff for men, with no BMI adjustment, because this calculator's source material does not specify body-size-adjusted bands for those two measures.
Why does the MMSE item use five score tiers instead of a single yes/no cutoff?
mmseDeficit is graded across five tiers rather than one pass/fail line: an MMSE under 10 scores a full deficit point of 1, 10-17 scores 0.75, 18-20 scores 0.5, 21-23 scores 0.25, and 24 or above scores 0 (no deficit). This graded scoring reflects that cognitive impairment exists on a spectrum rather than a single binary state — someone scoring 19 is meaningfully different from someone scoring 6, and a single cutoff would treat both identically as 'impaired' when the underlying deficit accumulation differs substantially.
Can this calculator diagnose frailty on its own?
No. This is a large, 40-item geriatric/clinical assessment instrument for researchers, clinicians, and geriatric-care contexts assessing accumulated health deficits — not a diagnostic tool on its own and not a rule for making an individual treatment decision. It is meant for risk stratification, research, and care-planning discussions, alongside clinical judgment, not a standalone diagnosis. Its items and cutoffs follow the published Searle et al. 2008 table directly, aside from one plain-language reword of the comorbidity middle label ('Possible or unconfirmed diagnosis' for the source's undefined 'Suspect') — one more reason to treat the output as decision support, not a final answer.
References
- Searle et al., A standard procedure for creating a frailty index, BMC Geriatrics. 2008;8:24
- BMC Geriatrics — full text of Searle et al. 2008 (open access)
- Fried et al., Frailty in Older Adults: Evidence for a Phenotype, J Gerontol A Biol Sci Med Sci. 2001
- Rockwood & Mitnitski, Frailty in Relation to the Accumulation of Deficits, J Gerontol A Biol Sci Med Sci. 2007
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.