Printed on 3/17/2026
For informational purposes only. This is not medical advice.
CURB-65 is a clinical prediction rule for estimating mortality risk in community-acquired pneumonia (CAP). It helps clinicians decide whether a patient can be treated as an outpatient or requires hospital admission. The score evaluates five criteria: Confusion, BUN, Respiratory rate, Blood pressure, and age ≥65.
Formula: CURB-65 = Confusion(1) + BUN>19(1) + RR≥30(1) + BP low(1) + Age≥65(1)
Evaluate confusion (new disorientation to person, place, or time), BUN > 19 mg/dL, respiratory rate ≥ 30/min, blood pressure (SBP < 90 or DBP ≤ 60), and age ≥ 65 years.
Each criterion present scores 1 point. The total score ranges from 0 to 5. Enter each finding into the calculator to generate the total.
Score 0–1: consider outpatient treatment. Score 2: consider short hospitalization or close outpatient follow-up. Score 3–5: hospitalize; scores 4–5 may warrant ICU consideration. For ICU patients, calculate [APACHE II](/tools/apache-ii-score) or [SOFA Score](/tools/sofa-score) for comprehensive severity assessment.
Emergency physicians, triage nurses
Rapidly assess pneumonia severity to determine whether a patient can be safely discharged with oral antibiotics or requires hospital admission for IV therapy and monitoring.
Hospitalists, internal medicine
Provide objective evidence to support admission decisions when the clinical picture is ambiguous. A CURB-65 of 2+ provides justification for inpatient care.
Family medicine, urgent care
Use CRB-65 (without BUN) in outpatient settings to identify patients who need emergency referral versus those safe for home treatment with close follow-up.
Hospital quality teams
Track pneumonia severity scores across patient populations to benchmark outcomes, identify overtriage or undertriage patterns, and improve care protocols.
Hospital administrators, public health
During respiratory illness outbreaks, CURB-65 helps allocate limited hospital beds to the sickest patients while safely discharging lower-risk individuals.
All clinicians
Document objective severity assessment to support clinical decision-making, communicate with consulting services, and provide medicolegal documentation of disposition rationale.
In outpatient or prehospital settings, use CRB-65 (omitting BUN). A CRB-65 of 0 identifies very low-risk patients; CRB-65 ≥1 warrants hospital evaluation.
A 40-year-old with severe pneumonia, hypoxia, and bilateral infiltrates may score only 1 (for elevated BUN or tachypnea). Age-based criteria mean younger patients can be undertriaged. Always consider hypoxia and imaging.
CURB-65 doesn't include SpO2 or PaO2. An SpO2 <92% on room air is itself an indication for hospitalization, regardless of the CURB-65 score. Use [A-a Gradient](/tools/aa-gradient) to assess oxygenation deficits and [ABG Interpreter](/tools/abg-interpreter) for acid-base status.
CURB-65 doesn't account for COPD, heart failure, diabetes, or immunosuppression. Patients with significant comorbidities may need admission even with low CURB-65 scores. Assess cardiovascular risk with [ASCVD Risk Calculator](/tools/ascvd-risk) for patients with heart disease.
The Pneumonia Severity Index (PSI/PORT score) includes 20 variables and is more accurate but harder to calculate. CURB-65 is faster and preferred for bedside use; PSI may be better for research or detailed risk stratification.
Patients with CURB-65 of 2 have ~9% mortality and require careful clinical judgment. Consider social factors, ability to tolerate oral medications, follow-up access, and oxygen requirements.
Use a standardized assessment (Abbreviated Mental Test Score ≤8, or new disorientation to person/place/time, or [Glasgow Coma Scale](/tools/glasgow-coma-scale) if severely altered). Don't count chronic baseline confusion unless it's acutely worse.
BUN > 19 mg/dL equals urea > 7 mmol/L. Make sure you're using the correct threshold for your laboratory's reporting units. For comprehensive renal assessment, use [Creatinine Clearance](/tools/creatinine-clearance) or [eGFR Calculator](/tools/egfr-calculator).
CURB-65 is a snapshot. A patient with initial score of 1 who deteriorates over hours should be re-evaluated. Serial assessment is part of good clinical care.
Aspiration pneumonia and hospital-acquired pneumonia have different microbiology and may warrant admission regardless of CURB-65 score for appropriate antibiotic coverage.
CURB-65 was derived and validated by Lim et al. in a 2003 study published in Thorax involving over 1,000 patients with community-acquired pneumonia. It is endorsed by the British Thoracic Society (BTS) guidelines for CAP management and is referenced in IDSA/ATS and European Respiratory Society guidelines as a validated severity assessment tool.
Your CURB-65 score ranges from 0 to 5 and estimates 30-day mortality risk in community-acquired pneumonia. A score of 0 carries approximately 0.6% mortality risk, and a score of 1 carries approximately 2.7% — both considered low risk. A score of 2 corresponds to roughly 6.8–9.2% mortality (moderate risk). A score of 3 carries approximately 14.5% mortality, score 4 approximately 40%, and score 5 approximately 57% — all high risk.
The score directly informs disposition decisions. Patients with scores of 0–1 are generally safe for outpatient treatment with oral antibiotics. A score of 2 warrants consideration of short-stay hospitalization or closely supervised outpatient management. Scores of 3–5 require hospitalization, and scores of 4–5 should prompt consideration of intensive care unit admission.
Use this calculator when assessing an adult patient with community-acquired pneumonia (CAP) to determine the appropriate level of care — outpatient treatment, hospital ward admission, or ICU admission. It is recommended by the British Thoracic Society (BTS) and is widely used in emergency departments and primary care settings.
It is particularly useful for supporting safe discharge decisions in patients who appear clinically well — a CURB-65 score of 0–1 provides objective evidence to support outpatient management, reducing unnecessary hospitalizations. It is also valuable for triaging patients during periods of high hospital census or during pneumonia outbreaks when bed availability is limited.
CURB-65 does not account for important prognostic factors such as comorbidities (COPD, immunosuppression, heart failure), bilateral or multilobar infiltrates on imaging, pleural effusion, hypoxia (SpO2 or PaO2), lactate levels, or the specific causative pathogen. A young patient with severe hypoxia and bilateral infiltrates may score 0 on CURB-65 if they are not confused, have normal BUN, normal respiratory rate, and normal blood pressure.
The score was developed and validated for community-acquired pneumonia and should not be applied to hospital-acquired pneumonia, ventilator-associated pneumonia, or pneumonia in immunocompromised patients (e.g., HIV, transplant recipients, chemotherapy patients), where different severity assessment tools are needed. The Pneumonia Severity Index (PSI/PORT score) is a more comprehensive alternative that incorporates comorbidities and laboratory data, though it is more complex to calculate. Clinical judgment should always supplement the CURB-65 score, especially when the score seems discordant with the patient's overall clinical appearance.
For related assessments, see Glasgow Coma Scale, APACHE II Score and SOFA Score.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
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