CURB-65 is a five-item clinical prediction score developed to help assess mortality risk in adults with community-acquired pneumonia. Its name refers to Confusion, Urea, Respiratory rate, Blood pressure and age 65 or older. Each present criterion adds one point, producing a score from 0 to 5.
This score is an aid for trained clinicians, not a diagnosis or a stand-alone instruction about where someone should receive care. Pneumonia can be serious even with a low score, and urgent symptoms require prompt medical assessment. The calculator asks whether each criterion is present; it does not measure or verify the findings.
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How to Use This Calculator
Use clinical findings obtained during an assessment for suspected community-acquired pneumonia.
Select Yes only when the corresponding CURB-65 definition is met: new confusion, blood urea above 7 mmol/L, respiratory rate at least 30 per minute, systolic pressure below 90 mmHg or diastolic pressure no higher than 60 mmHg, or age at least 65 years.
No is selected initially for every item. Review all five choices and change a criterion to Yes only when it is present.
Select Calculate. The page adds one point for each Yes answer and displays a neutral score band.
The original score uses serum urea above 7 mmol/L. A commonly quoted approximate equivalent is BUN above 19 mg/dL, but laboratory naming and units must be checked. Confusion in the derivation study was based on a defined mental-test score or new disorientation, not simply tiredness or worry.
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Formula Used
CURB-65 score = C + U + R + B + 65, where each component is 1 when present and 0 when absent.
The five thresholds are: confusion; urea >7 mmol/L; respiratory rate ≥30/min; systolic blood pressure <90 mmHg or diastolic blood pressure ≤60 mmHg; and age ≥65 years. The total ranges from 0 to 5.
The original 2003 derivation and validation study found increasing mortality across higher scores, but a score does not calculate an individual's personal probability. Different populations, treatment eras and clinical settings can change observed risk. Current adult pneumonia guidance favors a validated prognosis rule, especially the Pneumonia Severity Index, alongside clinical judgment when deciding whether hospitalization is needed.
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Variables Explained
Component
One-point definition
C — Confusion
New mental confusion meeting the clinical definition used for assessment.
U — Urea
Blood urea greater than 7 mmol/L (approximately BUN greater than 19 mg/dL).
R — Respiratory rate
30 breaths per minute or more.
B — Blood pressure
Systolic below 90 mmHg or diastolic at or below 60 mmHg.
65 — Age
Age 65 years or older.
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Worked Example
Consider a 72-year-old adult with community-acquired pneumonia whose respiratory rate is 32 per minute. They have no new confusion, urea is not above the threshold, and blood pressure is 118/70 mmHg.
Confusion = 0, urea = 0, respiratory rate = 1, low blood pressure = 0 and age ≥65 = 1. The total is 0 + 0 + 1 + 0 + 1 = 2.
The number summarizes only these five findings. A clinician would still consider oxygen level, ability to take oral medication, other illnesses, imaging and laboratory results, social support and the overall appearance of the patient. The page's label for a score of 2 should not be treated as an automatic admission order.
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Why Use This Calculator?
Higher scores were associated with higher mortality in the cohorts used to develop and validate CURB-65. The score is most useful as one structured part of an adult community-acquired pneumonia assessment. It was not designed for self-diagnosis, for children, or for every type of respiratory infection.
The page labels 0–1 as the lower score band, 2 as the intermediate score band and 3–5 as the higher score band. These neutral bands do not determine care location. They do not incorporate low oxygen saturation, severe comorbidity, inability to maintain oral intake, pregnancy, immune status or practical barriers to safe home care. A clinician may recommend hospital care at a low score or outpatient care at a higher score after considering the full situation.
Seek urgent medical help for severe difficulty breathing, blue or grey lips, collapse, marked drowsiness, rapidly worsening confusion or other emergency signs, regardless of the calculated score.
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Common Mistakes
Assuming default No means the finding was assessed: confirm every criterion from the clinical information before calculating.
Confusing urea and BUN: confirm both the analyte and unit on the laboratory report.
Missing threshold details: systolic must be below 90, while diastolic qualifies at 60 or below.
Using chronic cognitive impairment as new confusion: establish the current change and clinical definition.
Using the score outside its intended setting: it was developed for adults with community-acquired pneumonia.
Treating the result as a treatment order: disposition and treatment require clinical judgment and other findings.
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Frequently Asked Questions
Can I use CURB-65 to decide by myself whether pneumonia is serious?
No. It summarizes five clinical findings and cannot diagnose pneumonia or detect every reason someone needs urgent care. A healthcare professional should interpret it with the full assessment.
What is the difference between urea and BUN in this score?
The original threshold is urea greater than 7 mmol/L. BUN is reported differently; about 19 mg/dL is a commonly used equivalent. Confirm the test name and unit rather than copying the number alone.
Does a diastolic pressure of exactly 60 mmHg score a point?
Yes. The blood-pressure component is present when systolic pressure is below 90 mmHg or diastolic pressure is 60 mmHg or lower.
What do the lower, intermediate and higher score bands decide?
They only group the numerical score. They do not decide admission, discharge or intensive care; those decisions require the complete clinical assessment.
Is CURB-65 intended for children?
No. It was derived and validated for adults with community-acquired pneumonia. Pediatric assessment uses different age-specific clinical approaches.
Does a low score rule out the need for hospital care?
No. Oxygenation, comorbidities, complications, oral intake, support at home and clinical judgment can all change the appropriate care setting.
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