Bell score: ME/CFS disability scale
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The Bell CFIDS Disability Scale, rated 0 to 100
Your Bell score comes from the Bell CFIDS Disability Scale, a functional capacity rating developed by Dr David Bell, a clinician and researcher who spent decades working with ME/CFS patients. It provides a single score from 0 to 100 that describes your overall level of functioning and activity limitation, where 100 represents no symptoms and full normal activity, and 0 represents severe symptoms with the patient bedridden and unable to care for themselves.
Unlike multi-item questionnaires, the Bell scale works by asking you to select the description that best matches your current level of functioning. This makes it very quick to complete and easy to understand. It is widely referenced in ME/CFS patient communities and advocacy literature, and is sometimes used informally alongside more formal instruments like the FSS.
The Bell scale is particularly useful as a simple, repeatable snapshot of functional status. Because it takes only a minute to complete, it lends itself to regular tracking. Many people with post-viral conditions use it weekly or monthly to maintain a record of their overall trajectory. For a much more detailed profile of what specific activities cost you, see the FUNCAP questionnaire. For the standard long COVID 0–4 grading, see the PCFS scale.
This is a free, interactive version. Select the description that best fits your current situation and see your score immediately. No sign-up or email is required.
Your Bell score
Your results over time
Complete this again in a few weeks and the change will show here.
Symptom scores change slowly. A monthly retake is enough to see a trend.
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Understanding your Bell scale score
What the score measures
It rates your overall level of functioning from 0 to 100 in steps of 10. Each step describes symptoms at rest and with activity, how much of a normal level of activity you manage, and how much work you could do. 100 means no symptoms and full activity; 0 means bedridden all the time and unable to care for yourself.
Dr David Bell published the scale in 1995, in The Doctor's Guide to Chronic Fatigue Syndrome. It is a set of descriptions rather than a questionnaire: you pick the one that fits best. It is widely used in ME/CFS clinics and research, including as an outcome in at least one current drug trial (NCT07724834), but we have not found a published study of its measurement properties.
Bell score interpretation
No. Each of its 11 steps is its own description, so there are no separate bands. The descriptions give activity as a share of what would be expected: close to 90% at 70, 70 to 90% at 60, about 70% at 50, 50 to 70% at 40, about 50% at 30 and 30 to 50% at 20. From 30 down, they describe being mostly confined to the house; at 10 and 0, bedridden.
What a Bell score of 100 means
No symptoms at rest or with exercise. Normal overall activity. Able to work full-time without difficulty.
What a Bell score of 90 means
No symptoms at rest. Mild symptoms with activity. Normal overall activity. Able to work full-time without difficulty.
What a Bell score of 80 means
Mild symptoms at rest, made worse by exertion. Activity only slightly restricted, and only for activities that need exertion. Able to work full-time, with difficulty in jobs that need exertion.
What a Bell score of 70 means
Mild symptoms at rest. Some limitation of daily activity, clearly noticeable. Overall functioning close to 90% of expected, except for activities that need exertion. Able to work full-time with difficulty.
What a Bell score of 60 means
Mild to moderate symptoms at rest. Limitation of daily activity, clearly noticeable. Overall functioning 70–90% of expected. Unable to work full-time in jobs involving physical labour, but able to work full-time in light work if hours are flexible.
What a Bell score of 50 means
Moderate symptoms at rest. Moderate to severe symptoms with exercise or activity. Overall activity reduced to 70% of expected. Unable to do strenuous work, but able to do light duties or desk work for 4–5 hours a day, with rest periods.
What a Bell score of 40 means
A score of 40 describes moderate symptoms at rest and moderate to severe symptoms with activity, overall activity at 50 to 70% of what would be expected, not being confined to the house, and being able to do light or desk work for 3 to 4 hours a day with rest periods.
What a Bell score of 30 means
Moderate to severe symptoms at rest. Severe symptoms with any exercise. Overall activity reduced to 50% of expected. Usually confined to the house. Unable to do any strenuous tasks. Able to do desk work for 2–3 hours a day, with rest periods.
What a Bell score of 20 means
Moderate to severe symptoms at rest. Unable to do strenuous activity. Overall activity 30–50% of expected. Rarely able to leave the house. In bed most of the day. Unable to concentrate for more than an hour a day.
What a Bell score of 10 means
Severe symptoms at rest. Bedridden most of the time. No travel outside the house. Marked cognitive symptoms that prevent concentration.
What a Bell score of 0 means
Severe symptoms all the time. Bedridden constantly. Unable to care for self.
What a change in score means
No minimal important change has been published for the Bell scale. Because it moves in steps of 10, one step is the smallest change it can record. Function in ME/CFS often varies from week to week, so a change is more convincing when it holds over several weeks than when it appears once.
What it does not measure
No. It is a single overall rating of function, not a diagnostic test. It does not show which activities cost you most, how long crashes after exertion last, or which symptoms dominate.
For a profile of what specific activities cost you, the FUNCAP questionnaire covers 27 activities in eight groups. The post-exertional malaise questionnaire looks at crashes after effort, and the PCFS scale is the standard functional grading in long COVID research. Our post-exertional malaise explainer covers why activity limits work the way they do.
Taking this to your GP or consultant
Bring your score, the date, and the description you chose, since the words carry more information than the number. A trend over months is more useful than a single score. ME/CFS specialists are likely to know the Bell scale; a GP may not, so read out the description rather than relying on the number. For work or disability assessments, pair it with a FUNCAP, which records limits activity by activity. See also preparing for a GP appointment.
Sources and licence
Based on: Bell DS. The measurement of disability. In: The Doctor's Guide to Chronic Fatigue Syndrome. 2nd ed. Perseus Books; 1995. p. 119–31.
- Bell DS. The measurement of disability. In: The Doctor's Guide to Chronic Fatigue Syndrome. 2nd ed. Perseus Books; 1995. p. 119–31.
- CD19-B cell depletion in PAIS-ME/CFS patients. ClinicalTrials.gov NCT07724834 (uses change in Bell score as an outcome).