How this calculator works
The Fatigue Severity Scale contains nine responses from 1 to 7 referring to the previous week. Use the authorised questionnaire to collect responses; this page contains short item cues only and calculates its mean and sum. It does not present a new paraphrased questionnaire as a validated instrument. Higher results describe greater reported impact of fatigue. The original study involved multiple sclerosis and systemic lupus erythematosus. A numerical result does not determine the cause of fatigue, and no diagnostic cut-off is added here. The result is an estimate for information only and is not medical advice.
Formula
FSS total = Q1 + ... + Q9. FSS mean = total/9. All nine answers must be present, each an integer from 1 to 7.
Worked example
Nine responses of 4 give a total of 36 and a mean of 4. Responses 1, 2, 3, 4, 5, 6, 7, 7 and 1 also total 36 and average 4.
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Frequently asked questions
Does a missing response count as zero?
No. Zero is outside the response scale. This tool requires all nine recorded responses.
Are the item cues the full questionnaire?
No. Use the original authorised instrument, with its instructions and wording, to collect responses. The cues identify where to enter each answer.
Does a high mean diagnose a disorder?
No. Fatigue has many causes. The original scale measures reported severity and impact; it is not a diagnosis.