Wells Score / PERC Rule Calculator

Calculate Wells score and check PERC rule criteria for pulmonary embolism risk.

About Wells Score / PERC Rule Calculator

The Wells score stratifies pretest probability, which then determines whether a D-dimer or imaging pathway is used. PERC is only valid in patients already assessed as low risk and requires every criterion to be negative. Applying PERC to a patient who is not low risk invalidates the rule entirely, which is the most common misuse of it.

Formula

Wells Score / PERC Rule

Wells sums weighted criteria; PERC requires all eight criteria to be negative

Wells score: Above 4 indicates pulmonary embolism likely in the two-tier version
PERC rule: Only applicable when pretest probability is already low

Worked example

With the default values below, Wells Score / PERC Rule Calculator returns Wells Score of 3.0. Change any input above and every figure here is recalculated in your browser.

Inputs used

Wells criteria present, excluding heart rate and canceraccepts 0–5: 1
Heart rateaccepts 20–250 bpm: 105 bpm
Active malignancyone of Yes, No: No
Ageaccepts 18–110 years: 48 years
Oxygen saturationaccepts 50–100 %: 96 %
Other PERC criteria presentaccepts 0–5: 0

Results

Wells Score: 3.0
Wells Risk Category: Pulmonary embolism unlikely
PERC Rule Fully Negative: No
PERC Criteria Positive: 1
Interpretation: Unlikely category — a D-dimer pathway is commonly used, per local protocol

Step by step

1Values used
2Wells Score / PERC Rule
3Wells Score= 3.0
4Wells Risk Category= Pulmonary embolism unlikely
5PERC Rule Fully Negative= No
6PERC Criteria Positive= 1
7Interpretation= Unlikely category — a D-dimer pathway is commonly used, per local protocol

Assumptions and limits

The result is derived only from the 6 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
This reproduces a published formula for educational and reference use only. It is not a diagnostic tool, does not account for individual clinical context, and must not be used to make or change treatment decisions. Clinical assessment by a qualified healthcare professional is always required. Suspected pulmonary embolism is a medical emergency. If you have chest pain, breathlessness or coughing blood, seek emergency care immediately. These scores are decision aids for clinicians working within local diagnostic protocols.
This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

This reproduces a published formula for educational and reference use only. It is not a diagnostic tool, does not account for individual clinical context, and must not be used to make or change treatment decisions. Clinical assessment by a qualified healthcare professional is always required. Suspected pulmonary embolism is a medical emergency. If you have chest pain, breathlessness or coughing blood, seek emergency care immediately. These scores are decision aids for clinicians working within local diagnostic protocols.

Frequently Asked Questions

How is Wells Score / PERC Rule calculated?

Wells sums weighted criteria; PERC requires all eight criteria to be negative The Wells score stratifies pretest probability, which then determines whether a D-dimer or imaging pathway is used. PERC is only valid in patients already assessed as low risk and requires every criterion to be negative.

Why does Wells Score / PERC Rule matter?

Applying PERC to a patient who is not low risk invalidates the rule entirely, which is the most common misuse of it.

What values do I need to enter?

This calculator takes 6 inputs: Wells criteria present, excluding heart rate and cancer, Heart rate, Active malignancy, Age, Oxygen saturation, Other PERC criteria present. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.