CURB-65 Score Calculator

CURB-65 is a clinical rule that grades the severity of community-acquired pneumonia and predicts 30-day mortality. It was published by Lim and colleagues in Thorax in 2003. You add one point for each of five findings: Confusion, Urea above 7 mmol/L, Respiratory rate of 30 or more, low Blood pressure, and age 65 or older. The total runs from 0 to 5.

You score 1 point for new mental confusion (an Abbreviated Mental Test of 8 or less, or new disorientation), 1 point for serum urea above 7 mmol/L (BUN above about 19.6 mg/dL), 1 point for a respiratory rate of 30 breaths per minute or more, 1 point for systolic blood pressure below 90 mmHg or diastolic of 60 mmHg or less, and 1 point for age 65 years or older. Each criterion is all or nothing, so the highest possible score is 5.

In the Lim 2003 cohorts, 30-day mortality was about 0.6% at score 0, 2.7% at 1, 6.8% at 2, 14.0% at 3, and 27.8% at 4 or 5 (scores 4 and 5 were reported together because few patients reached 5). A score of 0 to 1 is low severity and may be treated at home, a score of 2 is moderate and often warrants a short or supervised stay, and a score of 3 to 5 is high severity that should be managed in hospital with assessment for intensive care.

The original CURB-65 threshold is serum urea above 7 mmol/L, a unit used widely outside the United States. In the United States the same lab is reported as blood urea nitrogen (BUN) in mg/dL. To convert, divide BUN in mg/dL by 2.8 to get urea in mmol/L, so 7 mmol/L equals about 19.6 mg/dL of BUN. This calculator accepts either unit and applies the single 7 mmol/L cutoff after converting.

CRB-65 drops the urea criterion so it can be used without bloodwork, for example in primary care, at the cost of some accuracy. The Pneumonia Severity Index (PSI, also called the PORT score) uses around 20 variables and stratifies risk more finely but is slower to apply at the bedside. CURB-65 is a practical middle ground that needs only five inputs.

No. This tool is for education only and is not a substitute for professional medical advice, diagnosis, or treatment. CURB-65 is one input into the assessment of pneumonia and does not replace clinical judgment, vital-sign trends, oxygen saturation, comorbidities, or local protocols. Decisions about admission, antibiotics, and intensive-care referral should be made by a qualified clinician.