Fatigue Severity Scale Calculator

The FSS is a validated 9-item self-report questionnaire that measures the severity of fatigue and its impact on daily activities. Developed by Krupp et al. in 1989, it is widely used in clinical settings for patients with multiple sclerosis, lupus, fibromyalgia, Parkinson's disease, stroke, and other chronic conditions. Each item is scored from 1 (strongly disagree) to 7 (strongly agree).

The FSS score is the average of all 9 item responses. You sum the scores for all nine questions and divide the total by 9. The result ranges from 1 to 7, with higher scores indicating greater fatigue severity and a larger negative impact on daily functioning.

An FSS average score of 4 or above is generally considered the clinical threshold for significant fatigue. Scores at or above this level suggest that fatigue is meaningfully interfering with your daily activities and quality of life, and further evaluation by a healthcare professional is recommended.

A score below 4 suggests that fatigue is not significantly impacting your daily life. Healthy adults without chronic conditions typically score around 2.3, reflecting minimal fatigue interference. However, individual context and clinical judgment should always be considered.

The FSS was originally validated for multiple sclerosis (MS) and systemic lupus erythematosus (SLE), but its use has since been extended to many other conditions including rheumatoid arthritis, fibromyalgia, Parkinson's disease, stroke, depression, and chronic fatigue syndrome.

Other commonly used fatigue assessment tools include the Modified Fatigue Impact Scale (MFIS), the Epworth Sleepiness Scale, the Multidimensional Fatigue Inventory (MFI), and the Chalder Fatigue Scale. The FSS stands out for its brevity, ease of use, and strong validation across multiple chronic disease populations.

No — the FSS is a screening and assessment tool, not a diagnostic instrument. The results can help you and your healthcare provider understand the extent to which fatigue affects your life, but a clinical diagnosis requires a full medical evaluation. Always consult a qualified healthcare professional for medical advice.

The FSS can be completed periodically to track changes in fatigue severity over time, especially when monitoring the effects of treatment or disease progression. Many clinicians administer it at regular follow-up appointments. There is no fixed interval — your healthcare provider will advise on the appropriate frequency for your situation.