Wells Score Calculator for DVT & PE

Calculate the Wells score to estimate the pre-test probability of deep vein thrombosis (DVT) or pulmonary embolism (PE). The score guides whether further imaging such as D-dimer or ultrasound is warranted.

Wells' Criteria for DVT

Tick each criterion that applies. Nine clinical features score +1 point each; an equally or more likely alternative diagnosis subtracts 2 points.

2pointsModerate Risk
DVT Likely ~17% — Moderate pretest probability
Recommended next step

Order a D-dimer. If negative, DVT is excluded; if positive, proceed to compression ultrasound of the proximal veins.

Risk stratification
RiskScoreDVT prevalence
Low≤ 0~3%
Moderate← your result1 – 2~17%
High≥ 3~75%
Criteria breakdown
CriterionPoints
Active cancer (treatment within 6 months or palliative)+1
Paralysis, paresis, or recent plaster immobilization of the lower extremities+1
Recently bedridden ≥ 3 days or major surgery within 12 weeks requiring general or regional anesthesia+1
Localized tenderness along the distribution of the deep venous system+1
Entire leg swollen+1
Calf swelling ≥ 3 cm larger than asymptomatic side (measured 10 cm below tibial tuberosity)+1
Pitting edema confined to the symptomatic leg+1
Collateral superficial veins (non-varicose)+1
Previously documented DVT+1
Alternative diagnosis as likely or more likely than DVT-2
Total Wells score2
Wells' score: Sum the points of every criterion present. A score of ≤ 0 is low risk, 1–2 is moderate risk, and ≥ 3 is high risk. The score estimates pretest probability of DVT and guides whether to use D-dimer or proceed straight to imaging. It is a clinical decision aid, not a diagnosis — always interpret alongside clinical judgment.

How the Wells' Criteria Estimate DVT Probability

Deep vein thrombosis (DVT) is a blood clot that forms in a deep vein, most often in the leg. Because the clinical signs — swelling, pain, and tenderness — are shared with many benign conditions such as muscle strain, cellulitis, and Baker's cyst, clinicians cannot rely on symptoms alone. The Wells' Criteria for DVT turn a focused history and examination into a structured pretest probability that tells the clinician how likely DVT actually is before any test is performed.

The score is built from nine clinical features, each worth one point, plus a single powerful modifier: if an alternative diagnosis is judged as likely or more likely than DVT, two points are subtracted. The features capture the classic risk factors and examination findings — active cancer, recent immobilization or surgery, paralysis, localized venous tenderness, whole-leg swelling, calf asymmetry of at least 3 cm, pitting edema, dilated superficial collateral veins, and a history of prior DVT. The total score then maps to one of three risk bands.

Interpreting the Three Risk Bands

A score of 0 or less is low risk, with a DVT prevalence of roughly 3%. A score of 1 to 2 is moderate risk, where about 17% of patients have a DVT. A score of 3 or more is high risk, where the prevalence climbs to approximately 75%. These bands drive the diagnostic pathway: in low and moderate risk, a D-dimer blood test is the sensible first step — a negative result effectively rules out DVT, while a positive result triggers compression ultrasound. In high risk, the pretest probability is so high that a negative D-dimer would not be reassuring, so the clinician proceeds directly to imaging.

Clinical Use and Caveats

The Wells' Criteria are among the most widely validated clinical prediction rules in medicine and are recommended by NICE and other guidelines for the assessment of suspected DVT. They are quick to apply at the bedside and reduce unnecessary imaging. However, the score is a decision aid, not a diagnosis. The alternative-diagnosis item requires clinical judgment, and the criteria are best used in patients with suspected lower-limb DVT rather than upper-limb or catheter-related thrombosis. Always combine the score with the full clinical picture and local protocols.

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The Wells score is a clinical prediction rule used to estimate the pre-test probability of deep vein thrombosis (DVT) and pulmonary embolism (PE). It was developed to help clinicians decide which patients need further testing and to reduce unnecessary imaging in low-risk patients. Because DVT and PE are common, dangerous, and often clinically silent, a structured approach to risk stratification is essential.

The DVT Wells score

For DVT, the score assigns points for clinical features: active cancer (+1), paralysis or recent plaster immobilization of a leg (+1), recently bedridden for more than three days or major surgery within twelve weeks (+1), localized tenderness along the deep venous system (+1), entire leg swollen (+1), calf swelling more than 3 cm compared with the asymptomatic leg (+1), pitting edema confined to the symptomatic leg (+1), collateral superficial veins (+1), and a previous documented DVT (+1). An alternative diagnosis as likely as or more likely than DVT subtracts 2 points. A score of 0 or less is low probability, 1–2 is moderate, and 3 or more is high.

The PE Wells score

The PE version scores clinical signs and symptoms of DVT (+3), an alternative diagnosis less likely than PE (+3), heart rate over 100 (+1.5), immobilization for three or more days or surgery within four weeks (+1.5), previous DVT or PE (+1.5), hemoptysis (+1), and active cancer (+1). A score of 0–1 is 'PE unlikely' and 2 or more is 'PE likely'. The two-tier version is now the most commonly used because it maps cleanly onto the decision to order a D-dimer.

How the score guides testing

In patients with a low or unlikely Wells score, a negative D-dimer test can safely rule out DVT or PE without imaging. In patients with a high or likely score, D-dimer is not reliable enough and imaging — venous ultrasound for DVT or CT pulmonary angiography for PE — is indicated directly. This two-step approach reduces unnecessary radiation, cost, and patient anxiety while maintaining diagnostic safety.

Clinical caveats

The Wells score is a pre-test probability tool, not a diagnostic test. It must be combined with D-dimer and imaging to confirm or exclude the diagnosis. The score is most reliable when applied by an experienced clinician who can accurately judge whether an alternative diagnosis is more likely. Always use the score alongside clinical judgment and current guideline recommendations.

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Frequently Asked Questions