PERC Rule Calculator

Calculate the Pulmonary Embolism Rule-Out Criteria (PERC Rule) to identify PERC-negative versus PERC-positive patients in low-risk pulmonary embolism assessment.

Last updated on: April 1, 2026

Calculate PERC Rule

Select yes if age is 50 years or older.
Select yes if heart rate is 100 bpm or higher.
Select yes if oxygen saturation is below 95%.
Select yes if hemoptysis is present.
Select yes if estrogen use is present.
Select yes if there is a prior history of DVT or pulmonary embolism.
Select yes if unilateral leg swelling is present.
Select yes if there was recent surgery or trauma requiring hospitalization, typically within the past 4 weeks.

What the PERC Rule Measures

The Pulmonary Embolism Rule-Out Criteria (PERC Rule) is a bedside rule used in patients with low clinical suspicion of pulmonary embolism to identify those who may not need further PE testing.

To be PERC negative, all eight criteria must be negative. If any one criterion is positive, the patient is PERC positive and the rule does not exclude PE.

PERC Result Interpretation

PERC Negative: Score 0. All eight criteria are negative. In a patient with low pretest probability, this supports a rule-out pathway without further PE testing in appropriate settings.
PERC Positive: Score 1 or more. At least one criterion is positive. The PERC rule does not exclude PE, and further diagnostic evaluation may be required.

Guideline Context

The PERC Rule is designed for patients who already have low clinical pretest probability of pulmonary embolism.

It is not a general-purpose PE score for all patients and should be interpreted together with clinical judgment and the broader diagnostic pathway.

Practical Workflow

If all criteria are negative in a low-risk patient, the PERC rule may support stopping further PE testing.

If any criterion is positive, the rule is not satisfied, and the patient typically proceeds to the next step of PE evaluation.

This page has been medically reviewed by Dr. Khoulah Attia – PharmD, Immunology Specialist.

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