CURB-65 calculator for community-acquired pneumonia
For healthcare professionals and students. Check results against your local protocols and clinical judgement; this tool does not give medical advice.
This CURB-65 calculator scores the severity of community-acquired pneumonia in adults from five features: Confusion, Urea, Respiratory rate, Blood pressure and age 65 or over. Instead of ticking boxes, you type the actual values — urea in mmol/L or BUN in mg/dL, the breathing rate and the blood pressure — and the tool applies each cut-off for you, shows which criteria scored and gives the risk band from the current NICE guideline.
Switch to CRB-65 when there is no blood result, as in general practice or a telephone assessment. It is the same score without urea, out of four, with its own bands. Everything is calculated in your browser.
How to use the CURB-65 Calculator
- Choose CURB-65 (hospital, with a urea result) or CRB-65 (no blood test).
- Tick Confusion if the abbreviated Mental Test score is 8 or less or there is new disorientation in person, place or time.
- Enter the urea and pick urea mmol/L or BUN mg/dL.
- Enter the respiratory rate, systolic and diastolic blood pressure and age.
- Read the score, the risk band and the line-by-line criteria, then check any warnings before recording it.
CURB-65 Calculator features
Scores real values
Type measurements rather than ticking boxes, so a borderline value is scored by the exact published cut-off.
Urea or BUN
Urea in mmol/L or blood urea nitrogen in mg/dL, converted with 1 mmol/L urea = 2.801 mg/dL BUN.
CURB-65 and CRB-65
One switch between the hospital score and the version without a blood test, each with its own NICE risk bands.
Transparent working
Each criterion is listed with its value and whether it scored, plus a copyable one-line summary.
Sense checks
Flags inverted blood pressures, unit mix-ups, children, implausible rates and the BUN 19 versus 19.6 mg/dL difference.
CURB-65 criteria
Each criterion present scores one point, giving 0 to 5. The definitions below are those in NICE guideline NG250 (box 2), which follow the original derivation by Lim WS, van der Eerden MM, Laing R, et al. Thorax 2003;58(5):377–382, a study of 1,068 adults admitted with community-acquired pneumonia in the UK, New Zealand and the Netherlands.
| Letter | Criterion (1 point each) |
|---|---|
| C | Confusion: abbreviated Mental Test score 8 or less, or new disorientation in person, place or time |
| U | Raised blood urea: over 7 mmol/L (BUN over 19.6 mg/dL) |
| R | Raised respiratory rate: 30 breaths per minute or more |
| B | Low blood pressure: systolic less than 90 mmHg, or diastolic 60 mmHg or less |
| 65 | Age 65 years or more |
Risk bands for CURB-65 and CRB-65
The bands below are quoted from NICE NG250, Pneumonia: diagnosis and management (published 2 September 2025; checked 19 October 2026). NICE asks clinicians to use clinical judgement together with the score to judge low-, moderate- or high-severity disease, and links the score to shared decisions about place of care — read the guideline’s recommendations rather than treating a number as a disposition.
In the original paper, 30-day mortality rose from 0.7% at a score of 0 to 57% at a score of 5. These were the patients of that study; local populations, treatment and comorbidity differ.
| Score | CURB-65 (hospital, box 2) | CRB-65 (primary care, box 1) |
|---|---|---|
| 0 | Low risk (less than 3% mortality risk) | Low risk (less than 1% mortality risk) |
| 1 | Low risk (less than 3% mortality risk) | Intermediate risk (1% to 10%) |
| 2 | Intermediate risk (3% to 15%) | Intermediate risk (1% to 10%) |
| 3 | High risk (more than 15%) | High risk (more than 10%) |
| 4–5 | High risk (more than 15%) | High risk (4 is the maximum) |
Urea, BUN and the 19 mg/dL question
The score was built on blood urea in mmol/L. Urea (CH₄N₂O) carries two nitrogen atoms, so 1 mmol/L of urea corresponds to 2.801 mg/dL of blood urea nitrogen and the 7 mmol/L threshold equals 19.6 mg/dL BUN. Many US references round it to “BUN over 19 mg/dL”, which differs only for a BUN between 19.1 and 19.6 mg/dL. This calculator applies the original threshold and tells you when a value falls in that gap, so you can follow your own protocol.
Worked example: a 72-year-old with urea 8.2 mmol/L, respiratory rate 24/min and blood pressure 118/70 mmHg, not confused, scores U + 65 = 2, intermediate risk. The same patient with a respiratory rate of 30/min scores 3, high risk.
CURB-65 Calculator FAQ
How do you calculate the CURB-65 score?
Give one point each for confusion, urea over 7 mmol/L, respiratory rate of 30 or more, systolic pressure under 90 or diastolic 60 mmHg or less, and age 65 or over. The CURB-65 calculator above applies each cut-off to the values you type.
What is the difference between CURB-65 and CRB-65?
CRB-65 leaves out urea so it can be used without a blood test, mainly in primary care. It scores 0 to 4 and NICE gives it different risk bands: 0 low (under 1%), 1–2 intermediate (1–10%), 3–4 high (over 10%).
What urea level counts for CURB-65 in mg/dL?
Urea over 7 mmol/L, which is a BUN over 19.6 mg/dL. Some US sources round this to 19 mg/dL; the tool notes when your value lies between the two.
Does a CURB-65 score of 0 or 1 mean the patient can go home?
Not by itself. NICE describes 0–1 as low mortality risk and asks for clinical judgement, because hypoxia, pleural complications, comorbidities, pregnancy or social circumstances can make disease more severe than the score suggests.
Can CURB-65 be used for children or for hospital-acquired pneumonia?
No. It was derived in adults with community-acquired pneumonia; the tool warns when the age entered is under 18.
Is the blood pressure criterion systolic or diastolic?
Either: one point if systolic is below 90 mmHg or diastolic is 60 mmHg or less. For a quick mean arterial pressure from the same reading there is a MAP calculator.