CURB-65 Pneumonia Severity Calculator
CURB-65 pneumonia severity calculator. Scores confusion, urea, respiratory rate, blood pressure and age ≥65 for a 30-day mortality band. Educational only.
CURB-65 Pneumonia Severity Calculator
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How to use the CURB-65 calculator
Confirm pneumonia first
CURB-65 grades the severity of community-acquired pneumonia once it's diagnosed — it doesn't diagnose pneumonia. Use it after a clinical and, usually, radiographic diagnosis.
Tick each criterion met
One point each for new Confusion, Urea above 7 mmol/L, Respiratory rate of 30 or more, low Blood pressure, and age 65 or older — the letters that give the score its name.
Acknowledge, then read the band
The 0–5 total maps to an approximate 30-day mortality and a suggested care setting, from outpatient to hospital and possible intensive care.
Combine with clinical judgement
The score is a guide, not a rule. Oxygen levels, other illnesses, frailty and social circumstances also shape the admission decision, which a clinician makes.
CURB-65 — grading pneumonia in five questions
A five-letter severity score
Community-acquired pneumonia is one of the commonest reasons people are admitted to hospital, but most patients can be treated safely at home. The hard question at first contact is which patients are at real risk of dying and therefore need hospital — possibly intensive — care. CURB-65, derived by Lim and colleagues in 2003, answers it with five binary checks, each worth a point: new Confusion, raised blood Urea (above 7 mmol/L, equivalent to a BUN above roughly 19 mg/dL), a fast Respiratory rate (30 breaths a minute or more), low Blood pressure (systolic under 90 or diastolic 60 or below), and age 65 or older. The total, from 0 to 5, tracks closely with 30-day mortality: roughly under 1% at a score of 0–1, a few per cent at 2, and rising steeply to well over a quarter of patients at 4–5.
That mortality gradient translates into a simple disposition guide. A score of 0 or 1 marks low-risk patients who can usually be managed at home with oral antibiotics. A score of 2 is an intermediate group for whom a short hospital stay or closely supervised outpatient care is reasonable. A score of 3 or more identifies severe pneumonia warranting hospital admission, with 4 or 5 prompting assessment for intensive or high-dependency care. A simplified version, CRB-65, drops the urea test so it can be used in primary care without bloods.
"CURB-65 turns five bedside checks into a mortality estimate — and, crucially, into a decision about where a patient with pneumonia is safest treated."
What the score can't see
CURB-65 is deliberately simple, and that simplicity is both its strength and its limit. It says nothing directly about oxygen levels, which can be dangerously low even when the five criteria look reassuring, and it doesn't weigh comorbidities like heart failure, COPD, or immunosuppression that raise risk independently. It can under-grade severity in younger patients (who score zero for age yet can still be very unwell) and in those whose blood pressure or mental state is borderline. For these reasons every guideline frames CURB-65 as an adjunct to clinical judgement, not a substitute: the clinician integrates the score with oxygen saturation, the chest findings, the patient's other conditions, and their social situation before deciding on admission and antibiotics. Across the UK, Australia, much of Asia and beyond, it remains a fast, evidence-based way to bring structure to that judgement — but a worried patient with a cough, fever, and breathlessness should seek medical assessment rather than self-score, because severe pneumonia can progress quickly.
10 Facts About CURB-65
Derived in 2003 by Lim et al (Thorax).
Confusion, Urea, Respiratory rate, BP, age 65.
One point each; maximum score 5.
Tracks 30-day mortality from <1% to >25%.
0–1 low (home), 2 intermediate, 3–5 severe (admit).
Urea > 7 mmol/L ≈ BUN > 19 mg/dL.
CRB-65 drops urea for use without blood tests.
It grades pneumonia severity — it doesn't diagnose it.
It ignores oxygen levels and comorbidities — judge those too.
Used in BTS / NICE and international pneumonia guidelines.
Frequently asked questions
Confusion (new), Urea above 7 mmol/L, Respiratory rate of 30 or more per minute, Blood pressure that is low (systolic under 90 or diastolic 60 or below), and age 65 or older. Each present feature scores one point, for a total from 0 to 5. The score grades the severity of community-acquired pneumonia and helps decide where the patient should be treated.
As a guide: 0–1 is low risk and usually suitable for treatment at home; 2 is intermediate, often warranting a short hospital stay or closely supervised care; and 3–5 is severe, indicating hospital admission, with 4–5 prompting assessment for intensive or high-dependency care. These are starting points — the clinician weighs other factors before deciding.
CRB-65 is the same score without the urea component, so it needs no blood test and can be used in the community or a GP surgery. It runs from 0 to 4. CURB-65 includes urea and is used where bloods are available, typically in hospital. Both stratify mortality risk; CURB-65 is slightly more discriminating because it adds a laboratory measure of severity.
No, and that's an important limitation. A patient can have a low CURB-65 score yet a dangerously low oxygen saturation, which on its own can justify admission. Clinicians always check oxygen levels and the chest examination alongside the score. CURB-65 is a quick severity estimate, not a complete assessment, so it is used together with — not instead of — these other findings.
The mortality figures come from the original derivation and validation cohorts and have held up across many studies: risk rises steeply with score, from well under 1% at 0 to over a quarter of patients at 4–5. They are population averages for community-acquired pneumonia, so an individual's risk can differ depending on comorbidities and the cause of the pneumonia. The estimate is a guide to severity, not a personal prediction.
CURB-65 was derived and validated for community-acquired pneumonia. Hospital-acquired and ventilator-associated pneumonia have different organisms, risk profiles, and prognostic factors, so the score isn't validated for them and other assessments are used. Applying CURB-65 outside its intended setting risks under- or over-estimating severity.
Age 65 or over contributes a point, so a young adult automatically scores zero for age and may also have a normal blood pressure and mental state, giving a low total despite being significantly unwell. Severe pneumonia in younger people can be masked this way. This is one reason the score must be read alongside oxygen levels, the clinical picture, and judgement rather than used mechanically.
No. Pneumonia can worsen quickly, and several CURB-65 inputs (urea, accurate respiratory rate, blood pressure) need clinical measurement. If you have a cough, fever, and breathlessness, seek medical assessment rather than relying on a self-calculated score. This tool is educational, to show how clinicians grade severity, not to triage your own illness.
The Pneumonia Severity Index (PSI/PORT) is a more detailed 20-variable score that is slightly better at identifying low-risk patients but is cumbersome to calculate. CURB-65 trades a little discrimination for speed and ease, which is why it's so widely used at the bedside. Many hospitals use whichever their local guideline specifies; both are decision aids, not replacements for judgement.
No. The boxes you tick are processed only in your browser. Nothing is sent to a server, stored, or shared, and no account is required. The whole calculation runs on your device, so none of the information leaves it.
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