APACHE II Calculator

Score the APACHE II severity index from 12 acute physiology values plus age and chronic health points, then read the estimated ICU in-hospital mortality band.

Quick Facts

Score range
0 to 71 points
Acute Physiology Score (12 variables, 0-4 each) + age points (0-6) + chronic health points (0-5).
Timing
First 24 hours in the ICU
Enter the worst recorded value for each variable during that window.

Your Results

Calculated
APACHE II score
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Total points (0-71)
Acute Physiology Score
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12-variable subtotal
Age + chronic health
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Non-physiology points
Est. hospital mortality
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Original-study band

Ready

Enter the worst first-24-hour values, then calculate the APACHE II score.

About the APACHE II score

APACHE II (Acute Physiology and Chronic Health Evaluation II) is a severity-of-illness score used in intensive care. Published by Knaus and colleagues in 1985, it remains one of the most widely used ICU scoring systems. The score is built from the worst physiological measurements recorded during a patient's first 24 hours in the ICU and produces a single number from 0 to 71 that rises with the severity of acute illness.

How the score is built

The total is the sum of three parts:

  • Acute Physiology Score (APS): twelve variables each score 0 to 4 points based on how far they deviate from normal - temperature, mean arterial pressure, heart rate, respiratory rate, oxygenation (PaO2 when FiO2 is below 0.5, otherwise the alveolar-arterial gradient A-aDO2), arterial pH, serum sodium, serum potassium, serum creatinine, hematocrit, white blood cell count, and the Glasgow Coma Scale (scored as 15 minus the measured GCS).
  • Age points: 0 for age 44 or under, 2 for 45-54, 3 for 55-64, 5 for 65-74, and 6 for 75 and older.
  • Chronic health points: 5 points for a history of severe organ insufficiency or immunocompromise in a nonoperative or emergency postoperative admission, or 2 points for the same history in an elective postoperative admission.

One special rule applies: the creatinine points are doubled when acute renal failure is present. Adding the three parts together gives the APACHE II score.

Interpreting the result

Higher scores indicate more severe illness and, on average, higher in-hospital mortality. In the original study of nonoperative patients, approximate mortality rose from about 4% at 0-4 points to roughly 25% at 15-19, 55% at 25-29, and about 85% above 34 points. These bands are population estimates from the derivation cohort, not a prediction for any one person, and modern intensive care can differ from that 1980s cohort.

When to consult a professional

This tool performs the standard APACHE II arithmetic for education and record-keeping. It is not a diagnosis and does not direct treatment. Any clinical decision should rest with the treating team, who interpret the score alongside the diagnosis, trends over time, and the whole clinical picture.

Frequently Asked Questions

What is the APACHE II score and what range does it use?
APACHE II (Acute Physiology and Chronic Health Evaluation II) is an ICU severity-of-illness score. It sums points from 12 acute physiology variables, an age score, and a chronic health score, using the worst values from the first 24 hours after ICU admission. The total ranges from 0 to 71, and higher scores indicate more severe illness and higher predicted hospital mortality.
How is the APACHE II score calculated?
The score adds three parts. The Acute Physiology Score gives 0 to 4 points each for temperature, mean arterial pressure, heart rate, respiratory rate, oxygenation, arterial pH, sodium, potassium, creatinine, hematocrit, white blood cell count, and 15 minus the Glasgow Coma Scale. Age adds 0 to 6 points, and chronic health adds 2 or 5 points for severe organ insufficiency or immunocompromise. Creatinine points are doubled in acute renal failure.
What mortality does an APACHE II score predict?
In the original 1985 study, approximate nonoperative in-hospital mortality rose with the score: about 4 percent at 0 to 4 points, 15 percent at 10 to 14, 25 percent at 15 to 19, 40 percent at 20 to 24, 55 percent at 25 to 29, and roughly 85 percent above 34. These are population estimates, not an individual prognosis, and should be interpreted by a clinician alongside diagnosis and trajectory.

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