DVT Risk Score (Wells Criteria) Calculator

Check all criteria that apply to estimate DVT probability using the Wells scoring system. The calculator returns your risk category, estimated DVT prevalence, and recommended diagnostic next steps.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Evaluate Active Cancer
Indicate if the patient has active cancer (treatment ongoing, within 6 months, or palliative) for 1 point.
2
Assess Bedrest/Surgery
Mark if the patient has been bedridden for ≥3 days or had major surgery within 12 weeks requiring general/regional anaesthesia for 1 point.
3
Check Calf Swelling
Determine if calf swelling is >3 cm compared to the asymptomatic leg (measured 10 cm below tibial tuberosity) for 1 point.
4
Look for Collateral Veins
Indicate presence of collateral superficial veins (non-varicose) for 1 point.
5
Evaluate Entire Leg Swollen
Mark if the entire leg is swollen for 1 point.
6
Test Localized Tenderness
Assess for localized tenderness along the deep venous system for 1 point.
7
Check for Pitting Oedema
Indicate if pitting oedema is confined to the symptomatic leg for 1 point.
8
Assess Paralysis/Paresis
Mark if there is paralysis, paresis, or recent plaster immobilisation of lower extremities for 1 point.
9
Review Previous DVT
Indicate if the patient has a previously documented DVT for 1 point.
10
Consider Alternative Diagnosis
Subtract 2 points if an alternative diagnosis is at least as likely as DVT.
11
Review your results
The calculator will display the Wells Score, DVT risk category, estimated prevalence, and recommended next steps.

Example Calculation

A clinician is evaluating a patient with leg swelling and tenderness, but no history of DVT, cancer, or recent surgery. They need to calculate the Wells DVT risk score.

Active cancer (treatment ongoing, within 6 months, or palliative)

Bedridden ≥3 days or major surgery within 12 weeks requiring general/regional anaesthesia

Calf swelling >3 cm compared to asymptomatic leg

Collateral superficial veins (non-varicose)

Entire leg swollen

Localized tenderness along deep venous system

Pitting oedema confined to symptomatic leg

Paralysis, paresis, or recent plaster immobilisation of lower extremities

Previously documented DVT

Alternative diagnosis at least as likely as DVT

Results

Low

Tips

Combine with D-dimer for Moderate Risk

For patients with a moderate Wells score (1-2 points), D-dimer testing is highly recommended. A negative D-dimer can rule out DVT with high confidence, often avoiding the need for ultrasound.

Clinical Judgment Always Paramount

The Wells score is a clinical decision rule, not a definitive diagnosis. Always integrate the score with your full clinical assessment, patient history, and physical examination findings. Consult a licensed physician for diagnosis and treatment.

Consider Age for D-dimer Thresholds

For patients over 50, an age-adjusted D-dimer threshold (age × 10 ng/mL) can reduce unnecessary imaging for DVT. However, this adjustment is typically applied after the Wells score assessment.

Assessing DVT Risk: The Wells Criteria Calculator

The DVT Risk Score (Wells Criteria) Calculator is a vital clinical tool for healthcare professionals to assess the pre-test probability of Deep Vein Thrombosis. By evaluating nine key clinical criteria, this calculator generates a Wells score, categorizing patients into low, moderate, or high-risk groups. This classification is crucial for guiding appropriate diagnostic pathways, such as D-dimer testing or ultrasound, optimizing patient care and resource allocation in 2025. Always consult a licensed physician for diagnosis and treatment.

Understanding Venous Thromboembolism (VTE) Risk

Understanding Venous Thromboembolism (VTE) risk is essential for patient safety, as it encompasses both Deep Vein Thrombosis (DVT) and its potentially fatal complication, pulmonary embolism (PE). VTE affects a significant population, with up to 900,000 Americans diagnosed annually. Key risk factors include prolonged immobility (e.g., bed rest, long flights), major surgery (especially orthopedic), active cancer, hormonal therapy, and inherited clotting disorders. Recognizing these factors allows clinicians to implement prophylactic measures, such as anticoagulants or compression stockings, to reduce the incidence of VTE. The Wells Criteria provides a structured approach to assess an individual's immediate DVT risk, informing whether further diagnostic testing is warranted.

The Wells Criteria: Scoring for DVT Probability

The Wells Criteria for DVT is a clinical decision rule that assigns points to various signs, symptoms, and risk factors, providing a score that estimates the probability of Deep Vein Thrombosis. This score helps clinicians determine the most appropriate next diagnostic steps.

The scoring system works as follows:

Total Score = Sum of Points for Positive Criteria - Points for Alternative Diagnosis

Each of the following criteria adds 1 point:

Active cancer (treatment ongoing, within 6 months, or palliative)
Bedridden ≥3 days or major surgery within 12 weeks
Calf swelling >3 cm compared to asymptomatic leg
Collateral superficial veins (non-varicose)
Entire leg swollen
Localized tenderness along deep venous system
Pitting oedema confined to symptomatic leg
Paralysis, paresis, or recent plaster immobilisation of lower extremities
Previously documented DVT
Subtract 2 points if an alternative diagnosis is at least as likely as DVT.

The final score then dictates the risk category:

Score ≥3: High risk (DVT prevalence ~75%)
Score 1-2: Moderate risk (DVT prevalence ~17%)
Score ≤0: Low risk (DVT prevalence ~3%)

💡 Just as the Wells score assesses DVT risk, other medical calculators help evaluate systemic health markers. Our eGFR (Kidney Function) Calculator provides insight into renal health.

Clinically Assessing a Patient for DVT Risk

A 55-year-old patient presents to the emergency department with unilateral calf swelling and tenderness. They report no history of cancer, recent surgery, or previous DVT. Upon examination, the clinician notes localized tenderness along the deep venous system and calf swelling of 3.5 cm compared to the other leg. An alternative diagnosis (e.g., cellulitis) is considered less likely than DVT.

Localized Tenderness: +1 point
Calf swelling >3 cm: +1 point
All other criteria (active cancer, bedrest/surgery, collateral veins, entire leg swollen, pitting oedema, paralysis, previous DVT): 0 points each.
Alternative diagnosis at least as likely as DVT: 0 points (as DVT is considered more likely).

Total Wells Score: 1 + 1 = 2 points

This score of 2 places the patient in the Moderate Risk category for DVT, suggesting a DVT prevalence of approximately 17%. The recommended next step would be D-dimer testing, followed by an ultrasound if the D-dimer is positive.

💡 Understanding various physiological metrics is key to comprehensive patient assessment. Our Electrolyte Balance Calculator offers insights into another crucial aspect of a patient's health status.

Understanding Venous Thromboembolism (VTE) Risk

The Development of the Wells Criteria

The Wells Criteria for Deep Vein Thrombosis (DVT) was developed by Dr. P.S. Wells and his colleagues in the late 1990s and early 2000s, primarily at the University of Ottawa. Prior to its widespread adoption, the clinical assessment of DVT was often subjective and varied, leading to inefficiencies in diagnostic pathways. Dr. Wells' team aimed to create a standardized, objective clinical decision rule that could stratify patients based on their pre-test probability of DVT. Their research, published in prominent medical journals, demonstrated that combining easily ascertainable clinical factors into a simple scoring system significantly improved the accuracy of DVT assessment, guiding appropriate imaging and treatment pathways and ultimately reducing unnecessary testing and improving patient outcomes.

Frequently Asked Questions

What is the Wells Criteria for DVT risk assessment?

The Wells Criteria for DVT (Deep Vein Thrombosis) risk assessment is a clinical decision rule used by healthcare professionals to estimate the pre-test probability of a patient having DVT. It assigns points based on nine clinical factors, such as active cancer, localized tenderness, and leg swelling. The total score categorizes patients into low, moderate, or high-risk groups, guiding subsequent diagnostic steps like D-dimer testing or ultrasound, thus optimizing resource use and patient care.

How is the Wells score interpreted?

The Wells score is interpreted based on the total points accumulated from the clinical criteria. A score of 0 or less typically indicates a low probability of DVT (around 3% prevalence). A score of 1 or 2 suggests a moderate probability (around 17% prevalence), usually prompting D-dimer testing. A score of 3 or more indicates a high probability of DVT (around 75% prevalence), often warranting immediate imaging like ultrasound, regardless of D-dimer results.

What are the limitations of the Wells Criteria?

The Wells Criteria, while highly valuable, have limitations. It is a clinical prediction tool and not a diagnostic test; a low score does not definitively rule out DVT, nor does a high score confirm it. The criteria are less accurate in certain populations, such as pregnant women or those with recurrent DVT. Clinical judgment remains essential, and abnormal D-dimer levels or persistent symptoms often necessitate further investigation, regardless of the score.

What is a D-dimer test and how does it relate to the Wells score?

A D-dimer test is a blood test that measures D-dimer, a protein fragment produced when a blood clot dissolves in the body. It is often used in conjunction with the Wells score to rule out DVT. For patients with a low or moderate Wells score, a negative D-dimer test can effectively exclude DVT, avoiding the need for more invasive imaging. However, a positive D-dimer is non-specific and requires further investigation, especially with a higher Wells score.