CURB-65 Calculator — Pneumonia Severity & Admission

Q: What CURB-65 score requires hospital admission?

A score of 0-1 generally supports outpatient treatment, a score of 2 suggests considering hospital admission (or closely supervised outpatient treatment), and a score of 3-5 indicates hospitalization, with ICU assessment considered especially at scores 4-5. These are guidance thresholds, not a substitute for overall clinical judgment.

Q: How does CURB-65 compare to the Pneumonia Severity Index (PSI)?

Both estimate pneumonia severity and mortality risk. CURB-65 uses only 5 simple criteria and is quick to calculate at the bedside or in the emergency department. PSI (PORT score) uses around 20 variables including detailed comorbidities and lab values, and is generally considered more precise for identifying low-risk patients, at the cost of being more complex to calculate.

Q: What counts as the confusion criterion in CURB-65?

The confusion criterion is typically assessed with the Abbreviated Mental Test (AMT), where a score of 8 or less out of 10 indicates confusion, or simply new disorientation to person, place, or time relative to the patient's baseline.

Q: Does it matter if urea is measured in mmol/L or mg/dL (BUN)?

No — the criterion is equivalent whichever unit your lab reports. Urea greater than 7 mmol/L corresponds to a blood urea nitrogen (BUN) greater than approximately 19 mg/dL. Either threshold, crossed, contributes the same 1 point.

Q: Is a CURB-65 score of 0 always safe for outpatient treatment?

A score of 0-1 is associated with low 30-day mortality and generally supports outpatient management, but the score does not capture every relevant factor — oxygen saturation, ability to take oral medication, social support, and comorbidities should also be considered before finalizing a disposition decision.

Criterion	Present?	Points
CURB-65 Total	0

Score	30-Day Mortality Band	Disposition
0	≈1.5% (low-risk band)	Outpatient treatment
1	≈1.5% (low-risk band)	Outpatient treatment
2	≈9.2%	Consider hospital admission (short inpatient stay or closely supervised outpatient treatment)
3	≈22% (high-risk band)	Hospitalize; consider ICU assessment
4	≈22% (high-risk band)	Hospitalize; consider ICU, especially at this score
5	≈22% (high-risk band)	Hospitalize; consider ICU, especially at this score

📋

Walk-through

How to Use This Calculator

5 steps

1

Check Confusion

Check Confusion if the patient shows new disorientation to person, place, or time — often assessed with the Abbreviated Mental Test (AMT), where a score of 8 or less out of 10 counts. Contributes 1 point.

2

Check Urea / BUN

Check Urea if a blood urea level is above 7 mmol/L, equivalently a blood urea nitrogen (BUN) above about 19 mg/dL. Either unit's threshold counts the same way. Contributes 1 point.

3

Check Respiratory Rate

Check Respiratory rate if the patient's breathing rate is 30 breaths per minute or higher. Contributes 1 point.

4

Check Blood Pressure

Check Low blood pressure if systolic blood pressure is below 90 mmHg or diastolic blood pressure is 60 mmHg or below. Contributes 1 point.

5

Check Age, then Review the Result

Check Age if the patient is 65 or older. The result panel then shows the total CURB-65 score (0-5), the 30-day mortality risk band, and the risk tier. Switch to Mortality Risk for the score breakdown or Disposition Guidance for the full 0-5 reference table.

⚡

Reference

Formula & Methodology

1 formula

CURB-65 Point System (Lim et al. 2003)

Score = Confusion(1) + Urea>7mmol/L or BUN>19mg/dL(1) + RespRate>=30(1) + (SBP<90 or DBP<=60)(1) + Age>=65(1)

Each letter maps to a clinical criterion: C = Confusion, U = Urea above 7 mmol/L (or BUN above 19 mg/dL), R = Respiratory rate 30/min or higher, B = low Blood pressure (systolic under 90 mmHg or diastolic 60 mmHg or below), 65 = age 65 or older. Each present criterion contributes exactly 1 point, for a total score of 0 to 5. The original derivation and validation cohort (Lim WS et al., Thorax 2003) reports 30-day mortality as three grouped bands rather than six distinct per-score percentages: 0-1 points (~1.5%), 2 points (~9.2%), and 3-5 points (~22%).

✓

High YMYL

Trust, Methodology & Sources

Reviewed by Calculover Editorial Review · Updated 2026-07-22 · 2 sources

Editorial accountability

Author: Quinn Sumner - Editor

Owner: Quinn Sumner - Editorial owner

Reviewer: Calculover Editorial Review - Medical-source review

Last reviewed: 2026-07-22

Last verified: 2026-07-22

Data effective: 2026-07-22

Methodology

CURB-65 applies the validated five-point scoring system described in Lim WS et al. (Thorax 2003;58:377-382), derived and validated in an international cohort of adults with community-acquired pneumonia. The derivation/validation cohort reports 30-day mortality as three grouped bands (0-1 low ~1.5%, 2 intermediate ~9.2%, 3-5 high ~22%) rather than six distinct per-score percentages; this calculator reports those verified bands rather than fabricating precision the underlying data does not support.

Assumption: The calculator applies to adults presenting with community-acquired pneumonia, not hospital-acquired or aspiration pneumonia.

Assumption: Clinical criteria (confusion, urea/BUN, respiratory rate, blood pressure, age) are entered accurately by a clinician or based on actual lab and vital-sign values.

Assumption: 30-day mortality bands are population averages from the Lim 2003 cohort; individual risk varies with treatment, comorbidities, and other clinical factors not captured by the score.

Limitations & guidance

30-day mortality is reported as three grouped bands (0-1, 2, 3-5), not distinct per-score percentages, because the primary source does not reliably publish six discrete per-score rates.

Not validated outside community-acquired pneumonia — does not apply to hospital-acquired or aspiration pneumonia.

The confusion criterion requires clinical judgment (e.g. Abbreviated Mental Test) and cannot be objectively verified by this calculator.

Does not replace clinical assessment of oxygen saturation, comorbidities, ability to tolerate oral intake, or social support — all of which affect the actual disposition decision alongside the score.

Professional guidance: CURB-65 Score Calculator is for health education and calculation transparency only. It is not medical advice, diagnosis, treatment, medication guidance, emergency guidance, or a substitute for care from a licensed healthcare professional.

Primary sources

Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study (Lim WS et al., 2003) - Thorax / BMJ Publishing Group

British Thoracic Society Guidelines for the Management of Community Acquired Pneumonia in Adults - British Thoracic Society

📖

Glossary

Key Terms Explained

7 terms

CURB-65 A five-point clinical scoring tool that estimates 30-day mortality risk and guides hospital admission decisions for adults with community-acquired pneumonia, based on Confusion, Urea, Respiratory rate, Blood pressure, and age 65 or older. Developed by Lim and colleagues and published in Thorax in 2003.

Community-Acquired Pneumonia A lung infection acquired outside of a hospital or healthcare facility setting, as opposed to hospital-acquired (nosocomial) pneumonia. CURB-65 was derived and validated specifically in community-acquired pneumonia patients presenting to hospital.

BUN (Blood Urea Nitrogen) A blood test measuring the nitrogen portion of urea, a waste product of protein metabolism cleared by the kidneys. CURB-65 uses a urea threshold of 7 mmol/L, equivalent to a BUN of approximately 19 mg/dL — elevated levels can reflect dehydration or reduced kidney perfusion associated with more severe infection.

Confusion Criterion New disorientation to person, place, or time relative to the patient's cognitive baseline, often operationalized with the Abbreviated Mental Test (AMT) — a score of 8 or less out of 10 counts toward the CURB-65 confusion criterion.

Disposition The clinical decision about where a patient should be treated — outpatient (at home), inpatient (hospital ward), or intensive care unit (ICU) — based on their overall condition. CURB-65 provides disposition guidance banded by score, alongside clinical judgment.

30-Day Mortality The probability that a patient dies within 30 days of presentation, used as the outcome measure in the CURB-65 derivation and validation studies. It rises from roughly 1.5% at scores 0-1 to roughly 22% at scores 3-5.

Respiratory Rate The number of breaths a patient takes per minute. A rate of 30 or more breaths per minute is one of the five CURB-65 criteria and reflects the degree of respiratory compromise from the pneumonia.

👥

Scenarios

Real-World Examples

3 worked examples

🙂

Maria — Low-Risk, 42-year-old Female

Otherwise healthy, mild cough and fever, alert and oriented, normal vitals

Confusion No Urea > 7 mmol/L No Respiratory rate >= 30 No Low blood pressure No Age >= 65 No CURB-65 Score 0 30-Day Mortality ~1.5%

Maria has none of the five CURB-65 criteria, giving her a score of 0 and an estimated 1.5% 30-day mortality risk — the low-risk band. Outpatient treatment is generally appropriate, pending overall clinical assessment.

😐

Harold — Intermediate-Risk, 71-year-old Male

New mild disorientation and age over 65, vitals otherwise stable

Confusion Yes (+1) Age >= 65 Yes (+1) All other criteria No CURB-65 Score 2 30-Day Mortality ~9.2%

Harold's new confusion and age over 65 each contribute 1 point, giving a score of 2 and an estimated 9.2% 30-day mortality risk — the intermediate-risk band. Hospital admission should be considered, or closely supervised outpatient treatment if social support and follow-up are strong.

⚠️

Dorothy — High-Risk, 79-year-old Female

Confused, elevated urea, tachypneic, hypotensive, and over 65

Confusion Yes (+1) Urea > 7 mmol/L Yes (+1) Respiratory rate >= 30 Yes (+1) Low blood pressure Yes (+1) Age >= 65 Yes (+1) CURB-65 Score 5 30-Day Mortality ~22%

Dorothy meets all five criteria for a maximum score of 5, placing her in the high-risk band (~22% 30-day mortality). She should be hospitalized with explicit ICU-level assessment, given the score's guidance to consider ICU especially at scores 4-5.

📄

Deep Dive

Understanding the CURB-65 Pneumonia Severity Score

3 chapters · 4 min read

Community-acquired pneumonia ranges from mild illness treatable at home to a life-threatening emergency requiring intensive care. The CURB-65 score was developed to help clinicians quickly stratify that severity at the point of first assessment, using five simple criteria that can be checked at the bedside without waiting for extensive lab work.

How CURB-65 Was Developed

Lim and colleagues derived and validated CURB-65 from an international cohort of adults with community-acquired pneumonia, publishing the score in Thorax in 2003 as an extension of the earlier British Thoracic Society (BTS) rule. The five-item, five-point instrument scores Confusion, Urea above 7 mmol/L, Respiratory rate of 30 or more breaths per minute, low Blood pressure (systolic under 90 mmHg or diastolic 60 mmHg or below), and Age 65 or older — each contributing 1 point, with no caps or weighting between items.

The score has since been endorsed by the British Thoracic Society and widely adopted in emergency medicine and primary care internationally as a fast severity-assessment tool that does not require awaiting a full chemistry panel to begin triage.

How to Use a CURB-65 Score in Practice

A score of 0-1 is generally considered low risk and supports outpatient treatment. A score of 2 is intermediate risk and calls for considering hospital admission, or a closely supervised outpatient course if the patient has strong social support and follow-up access. A score of 3-5 is high risk and indicates hospitalization, with explicit consideration of ICU-level care, especially at scores of 4 or 5.

These are guidance thresholds, not an automatic disposition order — factors CURB-65 does not directly capture, such as oxygen saturation, ability to tolerate oral intake and medications, comorbid conditions, and the patient's home support situation, should always be weighed alongside the score.

Limits and What CURB-65 Cannot Tell You

The 30-day mortality figures published in the Lim 2003 derivation and validation cohort are reported as three grouped bands — roughly 1.5% for scores 0-1, 9.2% for score 2, and 22% for scores 3-5 — rather than a distinct percentage for every individual score. Several secondary sources circulate a six-row table listing a unique mortality percentage for each score 0 through 5, but these figures disagree with one another across sources and are not reliably traceable to the primary paper, so this calculator reports the verified three-band model instead of fabricating precision the underlying data does not support.

CURB-65 was derived specifically in community-acquired pneumonia and is not validated for hospital-acquired or aspiration pneumonia. It also does not replace individualized clinical judgment about oxygenation, comorbidities, or a patient's ability to safely manage at home — the more detailed Pneumonia Severity Index (PSI) is sometimes used alongside CURB-65 when a more granular assessment of low-risk patients is needed.

❓

Questions

Frequently Asked Questions

6 questions

What are the 5 CURB-65 criteria?+

CURB-65 stands for Confusion, Urea > 7 mmol/L (BUN > 19 mg/dL), Respiratory rate >= 30 breaths/min, low Blood pressure (systolic < 90 mmHg or diastolic <= 60 mmHg), and age 65 or older. Each present criterion contributes 1 point, for a total score of 0 to 5.

What CURB-65 score requires hospital admission?+

A score of 0-1 generally supports outpatient treatment, a score of 2 suggests considering hospital admission (or closely supervised outpatient treatment), and a score of 3-5 indicates hospitalization, with ICU assessment considered especially at scores 4-5. These are guidance thresholds, not a substitute for overall clinical judgment.

How does CURB-65 compare to the Pneumonia Severity Index (PSI)?+

Both estimate pneumonia severity and mortality risk. CURB-65 uses only 5 simple criteria and is quick to calculate at the bedside or in the emergency department. PSI (PORT score) uses around 20 variables including detailed comorbidities and lab values, and is generally considered more precise for identifying low-risk patients, at the cost of being more complex to calculate.

What counts as the confusion criterion in CURB-65?+

The confusion criterion is typically assessed with the Abbreviated Mental Test (AMT), where a score of 8 or less out of 10 indicates confusion, or simply new disorientation to person, place, or time relative to the patient's baseline.

Does it matter if urea is measured in mmol/L or mg/dL (BUN)?+

No — the criterion is equivalent whichever unit your lab reports. Urea greater than 7 mmol/L corresponds to a blood urea nitrogen (BUN) greater than approximately 19 mg/dL. Either threshold, crossed, contributes the same 1 point.

Is a CURB-65 score of 0 always safe for outpatient treatment?+

A score of 0-1 is associated with low 30-day mortality and generally supports outpatient management, but the score does not capture every relevant factor — oxygen saturation, ability to take oral medication, social support, and comorbidities should also be considered before finalizing a disposition decision.

Download a one-page PDF of your numbers instantly. Add your email to also get our occasional calculator tips — no spam, unsubscribe anytime. Privacy.

CURB-65 Pneumonia Severity Score

Clinical Criteria

Score & Risk

Score Breakdown

Risk Context

CURB-65 Disposition Reference Table

How to Use This Calculator

Check Confusion

Check Urea / BUN

Check Respiratory Rate

Check Blood Pressure

Check Age, then Review the Result

Formula & Methodology

Trust, Methodology & Sources

Key Terms Explained

Real-World Examples

Maria — Low-Risk, 42-year-old Female

Harold — Intermediate-Risk, 71-year-old Male

Dorothy — High-Risk, 79-year-old Female

Understanding the CURB-65 Pneumonia Severity Score

How CURB-65 Was Developed

How to Use a CURB-65 Score in Practice

Limits and What CURB-65 Cannot Tell You

Frequently Asked Questions

Get a branded PDF of your results

CURB-65 Pneumonia Severity Score

Clinical Criteria

Score & Risk

Score Breakdown

Risk Context

CURB-65 Disposition Reference Table

How to Use This Calculator

Check Confusion

Check Urea / BUN

Check Respiratory Rate

Check Blood Pressure

Check Age, then Review the Result

Formula & Methodology

Trust, Methodology & Sources

Key Terms Explained

Real-World Examples

Understanding the CURB-65 Pneumonia Severity Score

How CURB-65 Was Developed

How to Use a CURB-65 Score in Practice

Limits and What CURB-65 Cannot Tell You

Frequently Asked Questions

Get a branded PDF of your results

Keep Exploring

Related calculators

Guides & articles

Related Calculators