Clinical Calculators

Validated clinical scoring instruments spanning multiple condition categories, implementing standardized measures used in clinical trials, treatment guidelines, and routine patient assessment.

Evidence-Based Clinical Scoring Tools

A suite of validated clinical calculators covering psoriasis, atopic dermatitis, chronic urticaria, vitiligo, melasma, alopecia areata, hidradenitis suppurativa, hyperhidrosis, and cutaneous T-cell lymphoma, along with phototherapy and topical dosing tools and a treatment response calculator. Each tool implements a standardized scoring system used in clinical trials, treatment guidelines, and routine patient assessment to quantify disease severity and treatment response.

The calculators are free to use. They were developed in partnership by the Centre for Medical and Surgical Dermatology and Dermi(opens in a new tab), a Toronto company that makes clinical imaging software for dermatology practices.

Available Calculators

Select a calculator to begin scoring. Each tool includes a reference section with clinical background and primary literature.

Showing 25 of 25 calculators

Inflammatory Skin DiseasePASIScore: 0–72

Psoriasis Area and Severity Index

Calculate the Psoriasis Area and Severity Index (PASI) online. Grade erythema, induration, and desquamation with body surface area involvement across four regions, using standard PASI or the high-discrimination PASI-HD method.

Inflammatory Skin DiseaseBSAPercent: 0–100

Body Surface Area Affected

Calculate the percentage of body surface area affected by psoriasis or eczema using the rule of nines or the palm method. Includes the NPF severity thresholds, the PGA x BSA composite, and change from baseline.

Inflammatory Skin DiseaseGPPASIScore: 0–72

Generalised Pustular Psoriasis Area and Severity Index

A validated clinical tool for quantifying generalised pustular psoriasis severity, adapted from the PASI with pustulation replacing induration. Evaluates four body regions with standard and high-discrimination scoring modes.

Inflammatory Skin DiseaseGPPGAScore: 0–4

Generalised Pustular Psoriasis Physician Global Assessment

A physician-reported global assessment for grading generalised pustular psoriasis severity. Evaluates erythema, pustulation, and scaling on a 0 to 4 scale, with the total score derived from the mean of all three components.

Inflammatory Skin DiseaseNAPSIScore: 0–80

Nail Psoriasis Severity Index

Calculate the Nail Psoriasis Severity Index (NAPSI) online. Score nail matrix and nail bed psoriasis by quadrant for each fingernail, with optional toenail scoring and percent improvement from baseline for NAPSI 50, 75, and 90.

Inflammatory Skin DiseasePGAScore: 0–4

Physician Global Assessment for Psoriasis

Grade overall plaque psoriasis severity with the static Physician Global Assessment (PGA), also known as the sPGA or IGA. Includes 5-point and 6-point modes, treatment-success evaluation, and the PGA x BSA composite.

Inflammatory Skin DiseasePSSIScore: 0–72

Psoriasis Scalp Severity Index

Calculate the PSSI for scalp psoriasis from erythema, induration and desquamation grades multiplied by the scalp area involved. Includes change from baseline, PSSI 50 to PSSI 100 responses and the PSSI 12 trial threshold.

Inflammatory Skin DiseaseEASIScore: 0–72

Eczema Area and Severity Index

The recommended core instrument for measuring clinical signs of atopic dermatitis, endorsed by the HOME initiative. Evaluates four body regions across four severity characteristics with support for adult and pediatric weight sets.

Inflammatory Skin DiseasevIGA-ADScore: 0–4

Investigator Global Assessment for Atopic Dermatitis

Grade overall atopic dermatitis severity using the validated Investigator Global Assessment for Atopic Dermatitis (vIGA-AD), a 5-point scale from clear to severe. Includes treatment-success evaluation and the vIGA-AD x BSA composite.

VitiligoVASIScore: 0–100

Vitiligo Area Scoring Index

A quantitative clinical tool for evaluating vitiligo parametrically, using hand-unit area estimation and residual depigmentation grading across five body regions. The total body VASI (T-VASI) represents the sum across all regions.

VitiligoF-VASIScore: 0–3

Facial Vitiligo Area Scoring Index

A focused vitiligo severity measure restricted to the face, which accounts for approximately 3% of total body surface area. F-VASI is particularly important because facial vitiligo has the greatest impact on quality of life.

MelasmamMASIScore: 0–24

Modified Melasma Area and Severity Index

Calculate the mMASI for melasma from the area of involvement and darkness of the forehead, malar and chin regions. Includes the original MASI with homogeneity, change from baseline and the percentage improvement.

AlopeciaSALTScore: 0–100

Severity of Alopecia Tool

Calculate the SALT score for alopecia areata from the percentage of terminal hair loss in four weighted scalp views. Includes the S0 to S5 subclasses, change from baseline, SALT50 to SALT90 responses and the SALT 20 endpoint.

Hidradenitis SuppurativaIHS4Score: 0–100

International Hidradenitis Suppurativa Severity Score System

A validated dynamic scoring system for hidradenitis suppurativa that captures disease activity by counting three lesion types with weighted multipliers. Suitable for monitoring treatment response over time.

Hidradenitis SuppurativaHurleyStage: 1–3

Hurley Staging System

The oldest and most widely used classification for hidradenitis suppurativa severity. A qualitative, three-stage system based on the extent of abscesses, sinus tracts, and scarring, designed to guide surgical decisions.

Hidradenitis SuppurativaHS-PGAGrade: 0–5

Hidradenitis Suppurativa Physician's Global Assessment

Grade hidradenitis suppurativa with the HS-PGA from counts of abscesses, draining fistulas and inflammatory nodules. Assigns the six grades from clear to very severe and evaluates the HS-PGA response against a baseline grade.

Hidradenitis SuppurativaSartoriusScore: 0–200

Modified Sartorius Score

Calculate the modified Sartorius score for hidradenitis suppurativa from the regions involved, lesion counts, lesion distance and skin separation. Implements the 2009 form and the 2003 original, with change from baseline.

UrticariaUAS7Score: 0–42

Weekly Urticaria Activity Score

Calculate the weekly Urticaria Activity Score (UAS7) from a seven-day diary of wheal counts and itch severity. Reports disease activity bands, the HSS7 and ISS7 sub-scores, and the change from a baseline score.

HyperhidrosisHDSSGrade: 1–4

Hyperhidrosis Disease Severity Scale

Rate hyperhidrosis severity with the HDSS, the single-item patient scale from 1 (never noticeable) to 4 (intolerable). Records the treated site and reports the 1-point and 2-point improvements from baseline used as trial responses.

PhototherapyFitzpatrickType: 1–6

Fitzpatrick Skin Type Classification

A numerical classification system (Types I-VI) for human skin based on its response to ultraviolet radiation. Widely used for phototherapy dosing, laser parameter selection, and skin cancer risk estimation.

PhototherapyNB-UVBDose: 0–5000

NB-UVB Dosing Calculator

Calculates narrowband UVB (311-313 nm) treatment time from Fitzpatrick skin type and measured irradiance. Includes a session-by-session dose escalation schedule following AAD-NPF phototherapy guidelines.

PhototherapyPUVAJ/cm2: 0–20

PUVA Dosing Calculator

Calculate oral PUVA dosing from body weight and Fitzpatrick skin type or minimal phototoxic dose. Includes the 8-MOP tablet dose, starting UVA dose, treatment-by-treatment increment schedule, and missed-treatment adjustments.

Topical TherapyFTUFTU: 0–40.5

Fingertip Unit Calculator

Calculate how much cream or ointment to apply using fingertip units for each body area and age group. Converts fingertip units into grams per application, per day, per week, and per course to guide prescribing.

Cutaneous LymphomamSWATScore: 0–400

Modified Severity Weighted Assessment Tool

Calculate the mSWAT skin score for mycosis fungoides and Sezary syndrome from the percentage of body surface area with patches, plaques and tumours in 12 regions. Includes change from baseline and the consensus response thresholds.

Treatment ResponseResponsePercent: 0–100

Treatment Response and Percentage Improvement

Calculate percentage improvement from baseline for PASI, PSSI, EASI, SCORAD, IHS4, VASI, F-VASI, NAPSI, SALT, BSA and mSWAT, and evaluate HiSCR from lesion counts. Reports each trial response threshold as reached or not reached.

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