How severe is my psoriasis today?
Grade the redness, thickness, and scaling of a representative plaque in each of four body regions, estimate the skin area involved, and get the Psoriasis Area and Severity Index — the same 0–72 score dermatologists and clinical trials use. Self-scoring is approximate, so the trend across saved scores matters more than any single number. Everything stays on this device.
Head & Neck
Upper Extremities
Trunk
Lower Extremities
Grading guide — what each grade means
Erythema (Redness)
How red is the patch? Look at the most typical plaque in this body region and compare its colour to the surrounding normal skin. Darker, more vivid red = higher grade. On darker skin tones, compare violet/purple/brown hues instead.
| Grade | Meaning |
|---|---|
| 0 · None | No redness; skin tone matches uninvolved area. |
| 1 · Light red | Slight pink discoloration, barely distinguishable from normal skin. |
| 2 · Red | Clearly red, but not deep red. Unmistakable on inspection. |
| 3 · Very red | Deep red, vivid discoloration across the plaque. |
| 4 · Extremely red | Deep fiery red, strongly pronounced, sometimes with a purplish hue. |
Induration (Thickness)
How raised is the patch above normal skin? Run your finger over the edge of a typical plaque. Flat = grade 0, barely palpable = grade 1. Very thick, sharply raised plaques = grade 4.
| Grade | Meaning |
|---|---|
| 0 · None | No palpable elevation — flush with surrounding skin. |
| 1 · Slight | Just palpable elevation (<0.25 mm). Can feel the edge but not see shadow. |
| 2 · Moderate | Clear elevation (0.25–0.5 mm). Visible raised border. |
| 3 · Marked | Thick, raised plaque (0.5–1 mm). Clearly elevated from several feet away. |
| 4 · Very marked | Very thick, very raised (>1 mm). Pronounced dome-like elevation. |
Desquamation (Scaling)
How much silvery flaking is on the patch? Look at how much of the plaque surface is covered by scale and how thick the scale is. Shiny/clean surface = grade 0. Thick cake-like scale covering the whole plaque = grade 4.
| Grade | Meaning |
|---|---|
| 0 · None | No scale visible; plaque surface is smooth or shiny. |
| 1 · Fine | Fine scale, only partial coverage of the plaque surface. |
| 2 · Moderate | Coarser scale, most of plaque covered but base still visible. |
| 3 · Coarse | Thick coarse scale covering the entire plaque surface. |
| 4 · Very coarse | Very thick, tenacious, cake-like scale. Prominent flaking. |
Area of region involved → area grade
| Involvement | Grade |
|---|---|
| 0% | 0 |
| <10% | 1 |
| 10–29% | 2 |
| 30–49% | 3 |
| 50–69% | 4 |
| 70–89% | 5 |
| 90–100% | 6 |
Total score → severity band
| Score | Band |
|---|---|
| 0 | Clear |
| 0–3 | Almost clear |
| 3–7 | Mild |
| 7–10 | Moderate |
| 10–20 | Severe |
| over 20 | Very severe |
Heads-up on the bands: the published instrument defines only the 0–72 score. The bands above are a common interpretive convention (another in wide use is under 10 mild, 10–20 moderate, over 20 severe). PASI 50/75/90 response thresholds are independent of the bands.
Source: Fredriksson T, Pettersson U. Severe psoriasis — oral therapy with a new retinoid. Dermatologica. 1978;157(4):238–244.
This is an educational self-assessment, not a diagnosis. PASI is a clinician-oriented instrument — self-scoring is approximate, and small grading differences between assessors are normal, so the trend across saved scores is what matters. Don’t start, stop, or change treatment on this number alone; discuss it with a dermatologist. Estimating extent is the hardest part — the BSA calculator lets you paint the affected area on a body map. And if you have joint pain, stiffness, or swelling alongside psoriasis, take the psoriatic arthritis screen.
Saved only on this device — and browsers erase site data. A history clear, a private window, or Safari's automatic deletion after seven days without a visit will take this log with it. The fix is a free DermApproved account: it backs this up automatically and puts it on every device you sign in to — details in how storage works.
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How the PASI calculator works
The Psoriasis Area and Severity Index — published by Fredriksson and Pettersson in Dermatologica in 1978 — is the standard yardstick of plaque psoriasis severity, used in clinics and in virtually every clinical trial. The body is divided into four regions weighted by their share of skin: head and neck (0.1), upper limbs (0.2), trunk (0.3), and lower limbs (0.4). In each region you grade three signs of a representative plaque from 0 to 4 — erythema (redness), induration (thickness), and desquamation (scaling) — and estimate how much of the region’s skin is involved, which maps to an area grade from 0 to 6. Each region contributes weight × (E + I + D) × area grade, and the four subtotals sum to a score from 0 to 72. The palm trick keeps the area step honest: your palm with fingers is roughly 1% of your total body surface, so you can count palms instead of guessing percentages.
Reading the number takes context. The published instrument defines only the score; the severity bands shown here are a widely used convention, and a PASI above 10 is the common marker of moderate-to-severe disease — usually read alongside body surface area and the DLQI quality-of-life score, the “rule of tens” — where phototherapy, systemics, and biologics enter the conversation. Treatment response is measured as percentage change: PASI 50, 75, and 90 mean the score has fallen at least that much from baseline, which is why a dated history beats any single reading. For a pure extent measure you can paint onto a body map, use the BSA calculator; and because roughly a third of people with psoriasis develop joint disease, the psoriatic arthritis screen is worth five minutes if you have joint pain or morning stiffness. Saved scores stay on this device and print as a one-page report for appointments.
Common questions
Is a self-scored PASI as reliable as one from my dermatologist?
It uses the exact same formula — the difference is in the grading, not the math. Induration (thickness) is the sign untrained scorers most often misjudge, and even trained assessors can differ by a few points on the same skin. That is why the trend across your own repeated scores, graded the same way each time, is more informative than comparing any single number against a clinic reading.
What PASI score counts as moderate-to-severe psoriasis?
A PASI above 10 is the threshold guidelines and trials most often use, typically read alongside a body surface area over 10% or a DLQI quality-of-life score over 10 — the “rule of tens.” Crossing it generally puts phototherapy, systemic drugs, or biologics on the table. Below 10, location still matters: plaques on the face, scalp, hands, or genitals can justify escalation at a lower score.
PASI 75, PASI 90, PASI 100 — what do the response numbers mean?
They describe change on treatment, not severity: PASI 75 means the score has fallen at least 75% from baseline, PASI 90 at least 90%, and PASI 100 means complete clearance. Trials report what fraction of patients reach each threshold, which is why the terms are all over biologic literature. Save a baseline score here and later saves are flagged when your own change crosses the 50, 75, or 90 mark.
How do I grade thickness on my own skin?
Run a fingertip from normal skin across the edge of a typical plaque. Flat and flush is grade 0; a rim you can feel but barely see is 1; a clearly raised border is 2; a plaque that visibly stands off the skin is 3; and a thick, dome-like plateau is 4. Grade the most representative plaque in each region, not the single worst spot.
Where do my saved scores go?
Into your own browser’s local storage on this device — nothing is sent to DermApproved or anywhere else. The trade-off is that clearing browser data erases the history, so if you’re tracking a treatment response worth keeping, download a backup from My Library. A dated series of scores is exactly what a dermatologist wants to see at a review appointment.