CURB-65 Calculator for Pneumonia Severity
Calculate the five CURB-65 criteria for adult community-acquired pneumonia using confusion, urea or BUN, respiratory rate, systolic and diastolic blood pressure, and age, with current NICE hospital risk groups.
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CURB-65 score
—
A population risk-stratification reference; not a diagnosis or treatment instruction.
Current NICE hospital risk group
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Population risk band, not an individual prediction or automatic action.
About
CURB-65 is a five-criterion mortality-risk stratification score for adults with clinically diagnosed community-acquired pneumonia (CAP) at hospital or initial acute-care assessment. Current NICE NG250 uses CURB-65 with clinical judgment for hospital adult CAP; the score does not diagnose pneumonia or provide an individual mortality probability. [1, 2]
This calculator uses the submitted confusion status, urea or BUN, respiratory rate, blood pressure, and completed age. It does not verify the CAP diagnosis, choose antibiotics or place of care, assess ICU need, or calculate CRB-65, PSI, or severe-CAP criteria. [2, 3, 4]
Formula
Interpretation
| CURB-65 score | NICE hospital group | Current NICE population band | Required boundary |
|---|---|---|---|
| 0–1 | Low | less than 3% 30-day mortality risk | not proof that outpatient care is appropriate |
| 2 | Intermediate | 3% to 15% | not an automatic admission rule |
| 3–5 | High | more than 15% | not an automatic ICU or treatment rule |
- CURB-65 score
- 0–1
- NICE hospital group
- Low
- Current NICE population band
- less than 3% 30-day mortality risk
- Required boundary
- not proof that outpatient care is appropriate
- CURB-65 score
- 2
- NICE hospital group
- Intermediate
- Current NICE population band
- 3% to 15%
- Required boundary
- not an automatic admission rule
- CURB-65 score
- 3–5
- NICE hospital group
- High
- Current NICE population band
- more than 15%
- Required boundary
- not an automatic ICU or treatment rule
These are current NICE 30-day population mortality-risk bands for hospital adults with CAP, not precise probabilities for an individual. The result surface reports the applicable band without converting it into an admission, discharge, ICU, antibiotic, or other treatment instruction. ATS/IDSA preferentially recommends PSI with clinical judgment when a prognostic rule is used for hospitalization decisions, while severe-CAP criteria answer a different question. [2, 3]
CURB-65 criteria and interpretation for adult CAP
What CURB-65 calculates
CURB-65 adds five one-point findings from the initial assessment of an adult with clinically diagnosed CAP. It reports a score from 0 to 5 and the corresponding current NICE hospital population risk group. Every input must be supplied; the page does not infer missing information or confirm the diagnosis. [1, 2]
Five CURB-65 criteria and exact point thresholds
Each criterion contributes one point only. New confusion means an abbreviated Mental Test Score of 8 or less or new disorientation in person, place, or time; stable chronic cognitive impairment without a new change does not automatically score. The BP item is one OR condition, so even when both pressure thresholds are met it contributes only one point. [1, 2]
| Criterion | One-point threshold | Submitted input used | Important boundary or limitation |
|---|---|---|---|
| Confusion | AMTS ≤8 or new disorientation | Yes / No | A stable previous impairment is not automatically new confusion. |
| Urea | >7 mmol/L | Urea mmol/L or BUN mg/dL | Strictly greater than 7; exactly 7 scores 0. |
| Respiratory rate | ≥30 breaths/min | Breaths/min | 29.9 scores 0; 30 scores 1. |
| Blood pressure | SBP <90 or DBP ≤60 mmHg | SBP and DBP in mmHg | One OR item, one point maximum; SBP 90 is not low. |
| Age | ≥65 completed years | Completed years | Age 64 scores 0; age 65 scores 1. |
- Criterion
- Confusion
- One-point threshold
- AMTS ≤8 or new disorientation
- Submitted input used
- Yes / No
- Important boundary or limitation
- A stable previous impairment is not automatically new confusion.
- Criterion
- Urea
- One-point threshold
- >7 mmol/L
- Submitted input used
- Urea mmol/L or BUN mg/dL
- Important boundary or limitation
- Strictly greater than 7; exactly 7 scores 0.
- Criterion
- Respiratory rate
- One-point threshold
- ≥30 breaths/min
- Submitted input used
- Breaths/min
- Important boundary or limitation
- 29.9 scores 0; 30 scores 1.
- Criterion
- Blood pressure
- One-point threshold
- SBP <90 or DBP ≤60 mmHg
- Submitted input used
- SBP and DBP in mmHg
- Important boundary or limitation
- One OR item, one point maximum; SBP 90 is not low.
- Criterion
- Age
- One-point threshold
- ≥65 completed years
- Submitted input used
- Completed years
- Important boundary or limitation
- Age 64 scores 0; age 65 scores 1.
Urea and BUN handling
The authoritative criterion is serum urea >7 mmol/L. For a BUN result, this page applies the fixed conversion shown in the Formula section and tests the unrounded normalized urea value; it does not replace the original threshold with a rounded “BUN >19” checkbox or claim extra laboratory precision. Changing the selected unit clears the prior value so the same number cannot be silently reinterpreted. [1, 2, 5]
CURB-65 vs CRB-65
CURB-65 includes serum urea and is the current NICE hospital mortality-risk score for adults with CAP. CRB-65 omits urea and is the separate NICE primary-care score. Missing urea does not turn a CURB-65 submission into CRB-65, and this page does not calculate or automatically fall back to that four-item model. [1, 2]
CURB-65 vs PSI and severe-CAP criteria
PSI/PORT is a separate multi-variable adult CAP prognostic model available on its own calculator page. ATS/IDSA preferentially recommends PSI with clinical judgment when a prediction rule is used to determine hospitalization need. ATS/IDSA severe-CAP major/minor criteria address ICU-level severity and are not interchangeable with either mortality score. [3, 4]
Important limitations
CURB-65 does not include oxygen saturation or oxygen requirement, sepsis, shock, respiratory failure, rapid deterioration, multilobar disease, pleural complications, major comorbidity, frailty, functional status, social support, ability to take oral medication, pregnancy context, immunosuppression, or treatment response. Children and people outside adult CAP at hospital or initial acute-care assessment need the relevant pathway. A clinically unstable or urgent presentation should not wait for an online score. Low does not prove that outpatient care is safe, and High does not automatically determine ICU care or treatment. [2, 3]
References
- Lim WS, van der Eerden MM, Laing R, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax. 2003;58(5):377–382. PMID 12728155. PMCID PMC1746657. DOI 10.1136/thorax.58.5.377.
- NICE NG250. Pneumonia: diagnosis and management. Published 2 September 2025; current recommendations page includes subsequent minor updates.
- Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. Am J Respir Crit Care Med. 2019;200(7):e45–e67. PMID 31573350. PMCID PMC6812437. DOI 10.1164/rccm.201908-1581ST.
- Fine MJ, Auble TE, Yealy DM, et al. A Prediction Rule to Identify Low-Risk Patients with Community-Acquired Pneumonia. N Engl J Med. 1997;336:243–250. PMID 8995086. DOI 10.1056/NEJM199701233360402.
- Labcorp. SI Unit Conversion Table. Blood urea nitrogen (BUN): conventional mg/dL to SI mmol/L factor 0.357; SI to conventional factor 2.80.
FAQ
For hospital adults with CAP, NICE describes scores 0–1 as Low with a less than 3% 30-day mortality population risk, 2 as Intermediate with 3% to 15%, and 3–5 as High with more than 15%. These are population bands used with clinical judgment, not individual probabilities or automatic actions.
Sources: [2]
The original and current NICE criterion is serum urea strictly greater than 7 mmol/L, so exactly 7 does not score. If BUN is entered, the calculator uses the fixed 0.357 mmol/L per mg/dL relationship shown on the page and tests the unrounded normalized urea value; it does not replace the source criterion with a rounded BUN checkbox or claim extra measurement precision.
PSI is a separate adult CAP prognostic model with many more demographic, comorbidity, examination, laboratory, and imaging variables. ATS/IDSA preferentially recommends PSI with clinical judgment when a prediction rule is used for hospitalization need; PSI cannot be calculated or inferred from a CURB-65 result.
The intended task is an adult with clinically diagnosed CAP at hospital or initial acute-care assessment. Children and people outside that context—including HAP, VAP, severe immunosuppression, and other distinct pneumonia pathways—should not be automatically mapped to this score. Pregnancy and important comorbid or social factors can also alter clinical decisions beyond the five inputs.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.