APACHE II Score Calculator

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Patient age in years. The APACHE II system applies to adults aged 16 and older.
years
Severe organ system insufficiency (liver, cardiovascular, renal, respiratory, or immunocompromised) present before this ICU admission.
Used with the Knaus logistic regression to estimate predicted mortality. Emergency postoperative patients have higher predicted mortality at any given score.
Worst rectal temperature recorded in the first 24 hours in the ICU, in degrees Celsius.
degC
Mean arterial pressure in mmHg. MAP = (SBP + 2 x DBP) / 3.
mmHg
Worst heart rate (beats per minute) in the first 24 hours.
bpm
Worst respiratory rate (breaths per minute) in the first 24 hours.
breaths/min
Fraction of inspired oxygen as a percentage. If >= 50%, enter the alveolar-arterial oxygen gradient (A-a DO2) below. If < 50%, enter the PaO2 below.
%
Arterial oxygen partial pressure. Only scored when FiO2 is less than 50%. Ignored when FiO2 >= 50%.
mmHg
Alveolar-arterial oxygen difference = PAO2 - PaO2. Use when FiO2 is >= 50%. PAO2 = (FiO2/100 x (Patm - 47)) - (PaCO2 / 0.8).
mmHg
Arterial blood pH. Worst value in the first 24 hours.
Serum sodium in mmol/L (same as mEq/L).
mmol/L
Serum potassium in mmol/L (same as mEq/L).
mmol/L
Serum creatinine in mg/dL. Points are doubled when acute renal failure is present.
mg/dL
Acute renal failure is defined as an acute rise in creatinine without prior chronic kidney disease. When present, the creatinine points are doubled.
Hematocrit percentage. Worst value in the first 24 hours.
%
White blood cell count in thousands per microliter (x10^3/uL), also written as 10^9/L. Worst value in the first 24 hours.
x10^3/uL
Total GCS score (3-15). Use the lowest GCS recorded in the first 24 hours. Score contribution = 15 minus actual GCS.
APACHE II ScoreLow severity
3

Total APACHE II score (0-71). Higher scores indicate greater severity of illness.

Predicted hospital mortality0%
Acute Physiology Score (APS)0
Age points3
Chronic health points0
3 pts
Low<9Moderate9-19High19-29Critical29+

APACHE II score 3 - predicted mortality 4.4% (nonoperative model).

  • The Acute Physiology Score (12 lab and vital variables) contributes 0 of the total 3 points.
  • Age adds 3 points to the score.
  • Scores below 15 generally correspond to lower acuity admissions, though individual patient trajectories vary widely.

Next stepAPACHE II predicts group-level mortality from admission data; it should not replace clinical judgment. Use the score alongside clinical assessment, not as a sole determinant of treatment intensity or goals of care.

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