What does a higher APACHE II score mean?

Higher scores indicate greater physiological derangement and predicted mortality. A score of 0–4 correlates with roughly 4% mortality, while a score above 35 correlates with over 85% mortality.

Which values should I use for each variable?

Use the worst (most abnormal) value measured during the first 24 hours in the ICU for each physiological variable.

Is this tool a substitute for clinical judgment?

No. APACHE II provides a statistical probability estimate across large populations. Individual patient outcomes depend on many factors. Always combine score interpretation with full clinical assessment.

What is the maximum possible APACHE II score?

The theoretical maximum is 71 points: 60 from the Acute Physiology Score, 6 from age, and 5 from chronic health status.

How is FiO2 used in the oxygenation score?

If FiO2 ≥ 0.5, the A-aDO2 gradient is scored. If FiO2 < 0.5, the PaO2 value is scored directly. Enter the FiO2 and the relevant value and the calculator will apply the correct rule.

APACHE II Score Calculator

Name: APACHE II Score Calculator
Availability: InStock
Author: Nham Vu

Enter 12 acute physiology variables, age, and chronic health status to calculate an APACHE II score and estimated ICU mortality risk.

Acute Physiology Variables

Enter the worst value in the first 24 hours for each parameter.

Vital Signs & Physiology

Temperature (°C)

Mean Arterial Pressure (mmHg)

Heart Rate (bpm)

Respiratory Rate (breaths/min)

Oxygenation

FiO₂ (fraction, 0.21–1.0)

A-aDO₂ (mmHg) (FiO₂ ≥ 0.5)

PaO₂ (mmHg) (FiO₂ < 0.5)

Laboratory Values

Arterial pH

Serum Sodium (mEq/L)

Serum Potassium (mEq/L)

Serum Creatinine (mg/dL)

Hematocrit (%)

WBC (×10³/mm³)

Neurological & Renal

Glasgow Coma Scale (GCS, 3–15)

Acute Renal Failure?

Age

Age Group

Chronic Health Status

Select the admission type and any pre-existing severe organ insufficiency or immunocompromise.

Admission Type

Liver: cirrhosis with portal hypertension, or biopsy-proven cirrhosis Cardiovascular: NYHA Class IV (severe restriction at rest or minimal activity) Respiratory: chronic restrictive, obstructive, or vascular disease limiting activity, or chronic hypoxia/hypercapnia/polycythemia/pulmonary hypertension (>40 mmHg) Renal: receiving chronic dialysis Immunocompromised: receiving immunosuppressive therapy, chemotherapy, steroids, or has leukemia, lymphoma, or AIDS

Fill in the values on the left and click Calculate.

APACHE II Score

out of 71

Estimated Hospital Mortality

—

Acute Physiology Score (APS) 0

Age Points 0

Chronic Health Points 0

Total APACHE II 0

Variable	Value	Points

This tool provides a statistical estimate only. APACHE II scores represent population-level mortality predictions and must not replace individual clinical assessment by a qualified clinician.

Summary

Enter 12 acute physiology variables, age, and chronic health status to calculate an APACHE II score and estimated ICU mortality risk.

How it works

Enter the worst value recorded in the first 24 hours for each of the 12 acute physiology variables.
Select the patient's age group from the dropdown.
Check any chronic health conditions that apply.
The calculator adds the Acute Physiology Score (APS), age points, and chronic health points.
The total APACHE II score (0–71) is displayed along with an estimated hospital mortality percentage.

Use cases

Estimate ICU patient mortality risk on admission.
Compare illness severity across patient populations for research.
Support clinical triage decisions in critical care units.
Track severity trends in ICU quality improvement programs.
Benchmark outcomes between institutions using a standardized score.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu