CURB-65 pneumonia severity calculator
Score five clinical criteria used to stratify mortality risk in adults with community-acquired pneumonia. Use the result with clinical judgment and local guidance.
Clinical inputs
Yes adds 1 point. Use new disorientation or a clinically defined confusion criterion.
Values greater than 19 mg/dL add 1 point in this calculator.
A rate of 30 breaths/min or more adds 1 point.
A systolic pressure below 90 mmHg contributes to the blood-pressure point.
A diastolic pressure below 60 mmHg contributes to the blood-pressure point.
Age 65 years or older adds 1 point.
Live result
CURB-65 score 2 of 5, intermediate risk tier, estimated mortality 6.8%.
Criterion breakdown
| Criterion | Observed value | Point threshold | Points |
|---|
How to use this CURB-65 calculator
What this calculator does
This calculator adds five binary clinical criteria to produce a CURB-65 score from 0 to 5 for adults with community-acquired pneumonia. It is designed for severity and mortality-risk stratification, not for diagnosing pneumonia or replacing a clinician's assessment. Current NICE pneumonia guidance recommends using clinical judgment together with CURB65 for adults with community-acquired pneumonia in hospital. The score is therefore best treated as one structured piece of a broader assessment that also considers oxygenation, comorbidity, complications, social circumstances, and the patient's overall clinical picture.
When to use it
Typical uses include checking the severity category after an adult has been assessed for community-acquired pneumonia, documenting how the five CURB-65 components contribute to the total, comparing a hand calculation with an electronic record, or creating an Excel copy of the current inputs and score for teaching or audit work. It is not intended for unsupervised self-triage, for children, or for hospital-acquired pneumonia.
How to calculate
- The calculator opens with a ready-to-use demonstration: no confusion, blood urea nitrogen 22 mg/dL, respiratory rate 32 breaths/min, systolic pressure 118 mmHg, diastolic pressure 72 mmHg, and age 58 years. The example result and its XLSX workbook are available immediately.
- Replace each demonstration value with the patient's measured or documented value. Inputs recalculate live; there is no separate Calculate button.
- Read the CURB-65 score, then review Estimated mortality, Risk tier, and Reference disposition. Use the criterion table to confirm which rules contributed points.
- Select Download Excel to export the current validated inputs, score, interpretation, and criterion breakdown to a real .xlsx workbook. Select Reset to clear the demonstration and all calculated content. After Reset, Download Excel is disabled until a complete valid set of inputs has been entered again.
Input guide
New-onset confusion is required and accepts Yes or No. Choose Yes only when the clinical definition of new confusion is met; Yes adds one point and No adds none. Blood urea nitrogen is required in mg/dL and accepts a plain decimal number from 0 to 300; 22 mg/dL is a realistic example, and values greater than 19 mg/dL add one point in this calculator. Do not paste units, commas, or scientific notation into this field. Respiratory rate is required as a whole number of breaths per minute from 1 to 100; 32 is the demonstration value, and 30 or more adds one point. Count breaths over an appropriate observation interval rather than entering an oxygen saturation percentage.
Systolic blood pressure and Diastolic blood pressure are both required whole numbers in mmHg. This implementation accepts systolic values from 40 to 300 and diastolic values from 20 to 200. A systolic value below 90 mmHg or a diastolic value below 60 mmHg adds the single blood-pressure point; meeting both conditions still adds only one point. The demonstration uses 118/72 mmHg. Age is required as a whole number from 18 to 120 years. An age of 65 years or older adds one point; the demonstration age is 58. Enter chronological age, not a date of birth or age range.
Output guide
CURB-65 score is the exact sum of the five criteria and ranges from 0 to 5. Estimated mortality is the reference calculator's reported mortality percentage for that score: 0.6% at score 0, 2.7% at score 1, 6.8% at score 2, 14.0% at score 3, and 27.8% at scores 4 or 5. Risk tier groups scores 0-1 as Low, 2 as Intermediate, and 3-5 as High. Reference disposition restates the source calculator's simple disposition category: outpatient treatment for 0-1, consider hospitalization for 2, and hospitalization required for 3-5. This text is a reproduction of the score interpretation, not individualized medical advice.
The Criterion breakdown table shows each criterion, the observed value, the threshold used, and whether it contributed 0 or 1 point. It is especially useful for boundary checks, such as a respiratory rate of exactly 30 or age of exactly 65, which both score a point. Because the selected calculator contract uses blood urea nitrogen in mg/dL and a strict diastolic threshold below 60 mmHg, do not silently substitute a differently worded local rule; compare with your clinical guideline when exact thresholds matter.
Worked example
In the opening example, confusion is No, so C contributes 0. Blood urea nitrogen is 22 mg/dL, which is greater than 19, so U contributes 1. Respiratory rate is 32 breaths/min, which is at least 30, so R contributes 1. Blood pressure is 118/72 mmHg, so neither pressure threshold is met and B contributes 0. Age is 58 years, below 65, so the age criterion contributes 0. The sum is therefore 0 + 1 + 1 + 0 + 0 = 2 / 5. The calculator displays an Estimated mortality of 6.8%, an Intermediate risk tier, and the reference disposition Consider hospitalization.
Understanding the score
CURB-65 is a prognostic rule developed for community-acquired pneumonia. The original derivation and validation work by Lim and colleagues is indexed by the U.S. National Library of Medicine. Each component contributes the same one-point weight, so the tool is intentionally simple: it does not attempt to model continuous risk changes within a criterion. For example, a respiratory rate of 30 and a much higher respiratory rate both contribute one point, even though the clinical implications may differ.
The five criteria are useful because they combine mental status, renal/biochemical information, respiratory physiology, circulation, and age in a compact score. However, important findings such as oxygen saturation, multilobar disease, sepsis features, frailty, pregnancy, immunosuppression, and ability to manage safely outside hospital are not directly represented. The British Thoracic Society pneumonia guidance resources provide broader clinical context for adult community-acquired pneumonia.
Interpreting results responsibly
A lower score generally corresponds to lower short-term mortality risk and a higher score to higher risk, but the score is not a stand-alone treatment order. A patient with a low CURB-65 score can still have features requiring urgent assessment, while a high score may coexist with goals of care or circumstances that change management. Use the numerical score to structure discussion and documentation, then integrate it with examination findings, investigations, response to initial treatment, and local escalation pathways.
For audit or education, the Excel export preserves the current typed inputs and the point-by-point breakdown. That makes it easier to verify whether a score came from the intended thresholds rather than from a transcription error. Because the calculator validates required inputs and rejects unsupported formats, a missing or malformed value does not silently become zero. Reset intentionally removes the startup demonstration, clears the score and breakdown, and prevents export until the assessment is complete again.
Medical safety: This calculator is for educational and clinical decision-support use. It does not diagnose pneumonia, predict an individual outcome with certainty, or replace professional assessment. Seek urgent medical care when a person has severe breathing difficulty, signs of shock, altered consciousness, or other emergency symptoms.