APACHE II Score Calculator

APACHE II ICU severity-of-illness score with predicted mortality (0–71).

For educational and clinical reference. Not a substitute for medical judgment. See the medical disclaimer.

Temperature — core (°C)

Mean arterial pressure (mmHg)

Heart rate (bpm)

Respiratory rate (breaths/min)

Oxygenation (A-aDO₂ if FiO₂ ≥ 0.5; else PaO₂)

Arterial pH

Serum sodium (mmol/L)

Serum potassium (mmol/L)

Serum creatinine (mg/dL) — doubled in acute renal failure

Hematocrit (%)

White blood count (×10³/mm³)

Glasgow Coma Scale (points = 15 − GCS)

Age (years)

Chronic health (severe organ insufficiency or immunocompromise)

Score

—

Interpretation

—

References

Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med. 1985;13(10):818-829.

What is APACHE II Score?

The APACHE II (Acute Physiology and Chronic Health Evaluation II) score is a severity-of-disease classification system used in intensive care units to predict hospital mortality. Published by Knaus et al. in 1985, it combines 12 routine physiologic measurements taken in the first 24 hours of ICU admission (such as temperature, mean arterial pressure, pH, sodium, creatinine, and the Glasgow Coma Scale) with age points and chronic health status. Scores range from 0 to 71; higher values indicate greater illness severity. A score of 25 corresponds to roughly 50% predicted mortality, though calibration varies by case-mix.

How to use

Select the worst value in the first 24 h for each physiologic variable.
Add the GCS-derived points, age, and chronic-health category.
The total APACHE II (0–71) and predicted mortality update instantly.

Frequently asked questions

What is APACHE II?

Acute Physiology and Chronic Health Evaluation II — an ICU severity-of-disease score (0–71) from 12 acute physiologic variables, age, and chronic health status.

When is APACHE II measured?

Using the worst values during the first 24 hours of ICU admission.

How is mortality estimated?

Higher scores predict higher hospital mortality; the precise prediction also incorporates the principal diagnosis via a disease-specific weight in the full model.

Why is creatinine sometimes doubled?

The creatinine point value is doubled in the presence of acute renal failure, reflecting its stronger prognostic weight.

Last updated June 28, 2026