BASDAI Calculator

Calculate Bath Ankylosing Spondylitis Disease Activity Index from six 0–10 patient-reported questions.

1.0M uses Updated · 2026-05-25 Runs locally · zero upload
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How to Use the BASDAI Calculator

Enter 0–10 scores for fatigue, spinal pain, peripheral joint pain, enthesitis, morning stiffness severity, and morning stiffness duration.

The calculator averages questions 5 and 6 first, then averages that stiffness score with questions 1–4. BASDAI of 4 or more commonly suggests active disease.

Formula and Method - BASDAI Calculator

BASDAI = (Q1 + Q2 + Q3 + Q4 + (Q5 + Q6) ÷ 2) ÷ 5

BASDAI converts patient-reported symptom severity into a 0–10 index. The two morning-stiffness questions are averaged so stiffness does not receive double weight.

Use Cases for the BASDAI Calculator

  • Monitoring ankylosing spondylitis or axial spondyloarthritis activity.
  • Comparing symptoms before and after treatment changes.
  • Helping patients quantify fatigue, pain, and morning stiffness before visits.

Frequently asked questions about BASDAI Calculator

Why average questions 5 and 6?

Both measure morning stiffness, so averaging prevents double weighting.

What does BASDAI ≥ 4 mean?

It is commonly used as a signal of higher disease activity, interpreted with clinical findings.

Can scores include decimals?

Yes. Decimal values between 0 and 10 are supported.