CURB-65 Calculator
CURB-65 pneumonia severity scored from real observations, with the mortality band and the place of care NICE recommends considering at each score.
CURB-65 Calculator: with the default inputs, curb-65 score is 1.
An abbreviated Mental Test score of 8 or less, or new disorientation in person, place or time.
Scores a point above 7 mmol/L — about 19.6 mg/dL of urea nitrogen.
Scores a point at 30 or more.
Scores a point below 90.
Scores a point at 60 or less.
Scores a point at 65 or over.
Out of 5.
- Risk of death
- Low risk
- Mortality risk in that band
- less than 3% mortality risk
- Place of care to consider
- NICE: consider discharge home, with referral to primary care-led services and safety netting advice.
- CRB65 score (without the urea)
- 1The primary-care version, out of 4.
- Urea in mmol/L
- 6
Assumptions
- This is an estimate for education. It does not diagnose anything and does not replace clinical judgement.
- The score applies only after a clinical diagnosis of community-acquired pneumonia has been made, in adults.
- Criteria and thresholds are those in NICE NG250, Box 2; the mortality bands and place-of-care options are NICE's.
- Urea converts at 1 mmol/L = 2.80 mg/dL of blood urea nitrogen, from the molar mass of urea (60.06 g/mol) and its two nitrogen atoms.
- The score does not include oxygenation, radiographic findings or comorbidities, and NICE notes it can be affected by comorbidities and pregnancy.
| Criterion | Observed | Point | |
|---|---|---|---|
| C | Confusion | AMT 8 or less, or new disorientation | 0 |
| U | Urea over 7 mmol/L | 6 mmol/L | 0 |
| R | Respiratory rate 30/min or more | 22 breaths/min | 0 |
| B | Systolic under 90 or diastolic 60 or less | 120/75 mmHg | 0 |
| 65 | Age 65 or over | 70 years | 1 |
Criteria as defined in NICE NG250, Box 2.
| CURB-65 | Risk of death | Place of care to consider | |
|---|---|---|---|
| 0 or 1 | Low — less than 3% | Discharge home with primary care-led follow-up and safety netting advice | ← this score |
| 2 | Intermediate — 3% to 15% | Virtual ward, same-day emergency care unit, hospital at home service, or inpatient care | |
| 3 to 5 | High — more than 15% | Inpatient care, with referral to critical care services if appropriate |
Bands and recommendations from NICE NG250. The score informs a shared decision about place of care; it does not make it.
How this is worked out
The formula
CURB65 — one point for each:
C Confusion (abbreviated Mental Test score 8 or less, or new disorientation
in person, place or time)
U Blood urea over 7 mmol/litre (about 19.6 mg/dL of urea nitrogen)
R Respiratory rate 30 breaths per minute or more
B Blood pressure: systolic under 90 mmHg, or diastolic 60 mmHg or less
65 Age 65 years or more
0 or 1 low risk — less than 3% mortality
2 intermediate risk — 3% to 15% mortality
3 to 5 high risk — more than 15% mortality
CRB65 is the same score without the urea, for use where no blood test is available.Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Confusion
- An abbreviated Mental Test score of 8 or less, or new disorientation in person, place or time.defaults to off
- Blood urea
- Scores a point above 7 mmol/L — about 19.6 mg/dL of urea nitrogen.from 0 to 100 · defaults to 6
- Urea units
- Choose one of 2 options.mmol/L urea (most countries) · mg/dL blood urea nitrogen (United States)
- Respiratory rate
- Scores a point at 30 or more.from 0 to 80 · whole numbers only · defaults to 22
- Systolic blood pressure
- Scores a point below 90.from 0 to 300 · defaults to 120
- Diastolic blood pressure
- Scores a point at 60 or less.from 0 to 200 · defaults to 75
- Age
- Scores a point at 65 or over.from 0 to 120 · whole numbers only · defaults to 70
What you get back
- CURB-65 scoremain answer
- Out of 5.
- Risk of death
- Mortality risk in that band
- Place of care to consider
- CRB65 score (without the urea)
- The primary-care version, out of 4.
- Urea in mmol/L
What this assumes
- This is an estimate for education. It does not diagnose anything and does not replace clinical judgement.
- The score applies only after a clinical diagnosis of community-acquired pneumonia has been made, in adults.
- Criteria and thresholds are those in NICE NG250, Box 2; the mortality bands and place-of-care options are NICE's.
- Urea converts at 1 mmol/L = 2.80 mg/dL of blood urea nitrogen, from the molar mass of urea (60.06 g/mol) and its two nitrogen atoms.
- The score does not include oxygenation, radiographic findings or comorbidities, and NICE notes it can be affected by comorbidities and pregnancy.
About this calculator
This is an estimate for education. It does not diagnose anything and does not replace clinical judgement.
What it does
CURB-65 is a severity score for community-acquired pneumonia. It assumes the diagnosis has already been made — it is not a test for whether someone has pneumonia — and sorts patients by their risk of dying within 30 days, which in turn informs where they should be cared for.
Five things score one point each: Confusion, raised Urea, raised Respiratory rate, low Blood pressure, and age 65 or over. The definitions used here are those in NICE NG250, which are the same thresholds the original derivation used.
Rather than asking you to tick boxes for the physiological items, this calculator takes the actual observations — urea, respiratory rate, blood pressure and age — and applies the thresholds itself. That removes one of the commoner sources of error, which is misremembering whether the blood pressure criterion is "or" (it is: systolic under 90 or diastolic 60 or less).
Reading the score
NICE bands the risk of death as:
- 0 or 1 — low risk, less than 3% mortality
- 2 — intermediate risk, 3% to 15%
- 3 to 5 — high risk, more than 15%
and pairs each band with a place of care to consider: discharge home with primary-care follow-up and safety netting at 0 or 1; a virtual ward, same-day emergency care unit, hospital at home service or inpatient care at 2; inpatient care with referral to critical care if appropriate at 3 or more.
The verb throughout NICE's recommendations is consider, and the framing is a shared decision with the patient. The score narrows the options; it does not choose between them.
Urea, and the unit trap
The threshold is a blood urea above 7 mmol/L. Laboratories in the United States report blood urea nitrogen instead, which is a different quantity — urea is 60.06 g/mol and carries two nitrogen atoms, so 1 mmol/L of urea is about 2.8 mg/dL of urea nitrogen, and the 7 mmol/L threshold is roughly 19.6 mg/dL of BUN. This calculator will take either; pick the right unit.
CRB65
Where no blood test is available — most of primary care — the urea is dropped, giving CRB65 out of 4. NICE bands it differently: 0 is low risk (under 1% mortality), 1 or 2 intermediate (1% to 10%), 3 or 4 high (over 10%), and it recommends considering referral to hospital at a CRB65 of 2 or more. Both scores are shown here.
What the score cannot see
Comorbidities, for one. NICE explicitly notes that the score can be affected by other factors including comorbidities and pregnancy. Hypoxia is not in it at all, and neither is anything about the chest radiograph. It weights age heavily enough that a fit 70-year-old scores a point for existing. And it was derived and validated in adults — children with community-acquired pneumonia are assessed differently.
Above all: anyone with symptoms or signs suggesting a more serious illness — cardiorespiratory failure, sepsis — should be referred regardless of what the score says.
Frequently asked questions
▸What does CURB-65 stand for?
Confusion, Urea over 7 mmol/L, Respiratory rate 30 or more, Blood pressure (systolic under 90 or diastolic 60 or less), and age 65 or over. One point each, maximum 5.
▸What does each CURB-65 score mean?
NICE bands 0 or 1 as low risk (under 3% mortality), 2 as intermediate (3-15%), and 3 to 5 as high risk (over 15%), with place of care ranging from discharge home to inpatient care with critical care referral.
▸What is the urea threshold in US units?
About 19.6 mg/dL of blood urea nitrogen, because 1 mmol/L of urea is roughly 2.8 mg/dL of urea nitrogen. This calculator converts either way.
▸What is the difference between CURB-65 and CRB65?
CRB65 drops the urea, for settings without a blood test. It is scored out of 4, and NICE bands it as 0 low, 1 or 2 intermediate, 3 or 4 high, with referral to hospital considered at 2 or more.
▸Does a low CURB-65 score mean someone can go home?
It means home care is reasonable to consider. NICE's wording is to use clinical judgement together with the score, and to refer anyone with signs of a more serious illness such as sepsis regardless of the score.
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