PASI Score Calculator
Calculate the Psoriasis Area and Severity Index (PASI) to quantify psoriasis severity across four body regions.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Step 1 of 6
How to Use This Calculator
- For each of the four body regions (Head, Arms, Trunk, Legs), enter Erythema, Induration, and Desquamation severity scores (0-4).
- Select the Area involvement score (0-6) for each region.
- The calculator applies the PASI area weighting factors (Head 0.1, Arms 0.2, Trunk 0.3, Legs 0.4).
- Review the Total PASI Score — above 10 indicates moderate-to-severe disease.
- Use PASI scores at baseline and follow-up to evaluate treatment response (PASI 75/90/100).
How the result changes with Trunk — Area
| Trunk — Area | Total PASI Score |
|---|---|
| 0.6 | 3.8 |
| 2.1 | 5.2 |
| 3.9 | 6.8 |
| 5.4 | 8.2 |
What each input means
- Head — Erythema
- Redness: 0=none, 1=slight, 2=moderate, 3=severe, 4=very severe.
- Head — Induration
- Thickness/plaque elevation: 0–4.
- Head — Desquamation
- Scaling: 0–4.
- Head — Area
- 0=0%, 1=<10%, 2=10-29%, 3=30-49%, 4=50-69%, 5=70-89%, 6=90-100%.
- Arms — Erythema
- Redness: 0–4.
- Arms — Induration
- Thickness: 0–4.
- Arms — Area
- Area: 0–6.
What each result means
- Total PASI Score
- Range 0–72. Higher = more severe.
- Severity Level
- 1=mild (<5), 2=moderate (5–10), 3=severe (>10).
- PASI 75 Target
- Score for 75% improvement.
- PASI 90 Target
- Score for 90% improvement.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersHead — Erythema = 1, Head — Induration = 1, Head — Desquamation = 1, Head — Area = 1 = 16 input(s) provided
- Calculate Total PASI ScoreTotal PASI Score = headScore + armsScore + trunkScore + legsScore5.1 = 5.1
- Calculate Severity Level2 = 2
- Calculate Head ComponentHead Component = (headErythema + headInduration + headDesquamation) * headArea * 0.10.3 = 0.3
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