Goal
Calculate the APACHE II arithmetic from 12 acute-physiology components, age points, and chronic-health points, with oxygenation mode and creatinine weighting made explicit.
APACHE II Severity Score Calculator
Calculate the APACHE II arithmetic from 12 acute-physiology components, age points, and chronic-health points, with oxygenation mode and creatinine weighting made explicit.
Key facts
- What it does
- Calculate the APACHE II arithmetic from 12 acute-physiology components, age points, and chronic-health points, with oxygenation mode and creatinine weighting made explicit.
- Formula
APACHE II = acute physiology score + age points + chronic-health points. The acute physiology score adds temperature, MAP, heart rate, respiratory rate, oxygenation, pH, sodium, potassium, creatinine, hematocrit, white-cell count, and (15 − GCS) using the APACHE II bands.- You enter
- Worst core temperature · Worst mean arterial pressure · Worst heart rate · Worst respiratory rate · Oxygenation variable · PaO₂ or A–aDO₂ value · Arterial pH · Serum sodium · Serum potassium · Serum creatinine · Acute renal failure doubling rule · Hematocrit · White-cell count · Glasgow Coma Scale · Age · Qualifying chronic-health status
- Worked example
- All entered values are in the zero-point bands, so APACHE II = 0 + 0 + 0 = 0 points.
A clearer path to an answer
From your question to a useful result
This page keeps the calculation transparent: define the goal, enter the matching values, inspect the method, and decide what the result means in your situation.
Inputs
Worst core temperature · Worst mean arterial pressure · Worst heart rate · Worst respiratory rate · Oxygenation variable · PaO₂ or A–aDO₂ value · Arterial pH · Serum sodium · Serum potassium · Serum creatinine · Acute renal failure doubling rule · Hematocrit · White-cell count · Glasgow Coma Scale · Age · Qualifying chronic-health status
Method
APACHE II = acute physiology score + age points + chronic-health points. The acute physiology score adds temperature, MAP, heart rate, respiratory rate, oxygenation, pH, sodium, potassium, creatinine, hematocrit, white-cell count, and (15 − GCS) using the APACHE II bands.
Next step
Calculate, review the assumptions below, then compare a related tool when the decision needs more context.
APACHE II Severity Score Calculator
Calculate the APACHE II arithmetic from 12 acute-physiology components, age points, and chronic-health points, with oxygenation mode and creatinine weighting made explicit.
Open the APACHE II Severity Score Calculator pageMore health tools
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Result
Enter your values above and choose Calculate to see the result here.
Calculation map
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01
Inputs (16)
- Worst core temperature Ready
- Worst mean arterial pressure Ready
- Worst heart rate Ready
- Worst respiratory rate Ready
- +12 more inputs
02
Formula
APACHE II = acute physiology score + age points + chronic-health points. The acute physiology score adds temperature, MAP, heart rate, respiratory rate, oxygenation, pH, sodium, potassium, creatinine, hematocrit, white-cell count, and (15 − GCS) using the APACHE II bands.
Bounded, transparent calculation
03
Result
- Calculate to preview the result.
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Formula, assumptions, and example
Formula: APACHE II = acute physiology score + age points + chronic-health points. The acute physiology score adds temperature, MAP, heart rate, respiratory rate, oxygenation, pH, sodium, potassium, creatinine, hematocrit, white-cell count, and (15 − GCS) using the APACHE II bands.
This page implements the published APACHE II point bands and makes two branches explicit: use PaO₂ when FiO₂ is below 0.5 or A–aDO₂ when FiO₂ is at least 0.5, and double creatinine points only when the qualifying acute-renal-failure rule applies. It reports arithmetic, not prognosis or treatment.
- Inputs represent the worst qualifying values in the specified assessment window, entered by trained clinical staff.
- Temperature is core temperature in degrees Celsius and blood pressure is entered as mean arterial pressure, not systolic pressure.
- The oxygenation mode is selected according to FiO₂ and the corresponding PaO₂ or A–aDO₂ value is entered in mmHg.
- Creatinine is entered in mg/dL and its APACHE point is doubled only when the acute renal failure rule is explicitly selected.
- GCS points are calculated as 15 minus the actual GCS, with GCS constrained to 3–15.
- Age and chronic-health points are added to the acute physiology score exactly as selected, with no mortality equation applied.
- The score is intended for trained ICU severity assessment and population-level comparison, not individual triage or treatment selection.
- Local protocols, source documentation, and qualified critical-care judgment take priority if they use a different version or handling rule.
Worked example: All entered values are in the zero-point bands, so APACHE II = 0 + 0 + 0 = 0 points.
Displayed input contract
- Worst core temperature · minimum 20 · maximum 45
- Worst mean arterial pressure · minimum 0 · maximum 250
- Worst heart rate · minimum 0 · maximum 300
- Worst respiratory rate · minimum 0 · maximum 100
- Oxygenation variable · 2 choices
- PaO₂ or A–aDO₂ value · minimum 0 · maximum 1000
- Arterial pH · minimum 6 · maximum 9
- Serum sodium · minimum 50 · maximum 250
- Serum potassium · minimum 1 · maximum 10
- Serum creatinine · minimum 0 · maximum 20
- Acute renal failure doubling rule · 2 choices
- Hematocrit · minimum 0 · maximum 80
- White-cell count · minimum 0 · maximum 100
- Glasgow Coma Scale · minimum 3 · maximum 15
- Age · minimum 0 · maximum 120
- Qualifying chronic-health status · 3 choices
The displayed limits are checked before the handler runs. Model-specific domain checks may also reject impossible or non-finite inputs.
Methodology: This calculator follows the WorldCalculate input, formula, precision, and boundary policy. Read the official methodology.
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Answer-first guide
How to use the APACHE II Severity Score Calculator for a real question
Calculate the APACHE II arithmetic from 12 acute-physiology components, age points, and chronic-health points, with oxygenation mode and creatinine weighting made explicit. Start with one clearly defined goal, enter values in the units shown, and keep the result attached to the assumptions below.
What this answers
This tool is useful when your question includes APACHE II calculator, APACHE 2 score, acute physiology score. It returns the outputs declared in the calculator contract rather than a live quote, approval, diagnosis, or professional sign-off.
What you enter
Worst core temperature · Worst mean arterial pressure · Worst heart rate · Worst respiratory rate · Oxygenation variable · PaO₂ or A–aDO₂ value · Arterial pH · Serum sodium · Serum potassium · Serum creatinine · Acute renal failure doubling rule · Hematocrit · White-cell count · Glasgow Coma Scale · Age · Qualifying chronic-health status. Keep the same time period, unit system, and currency wherever the form requires comparable values.
How to check it
Run the worked example first, compare its output with the page's example, then change one input at a time. This makes an unexpected result easier to trace to a unit, boundary, or assumption.
Three checks before you rely on the answer
- Match the question. Confirm that the result means the quantity you need, not a similar-sounding percentage, balance, rate, or estimate.
- Match the inputs. Use the requested units and period, and read each hint before replacing the example values with your own.
- Read the boundary. Review the assumptions and limits. Inputs represent the worst qualifying values in the specified assessment window, entered by trained clinical staff.
Need a wider view? Browse Health Calculators or compare the related tools below. The WorldCalculate methodology explains how formulas, examples, limits, and revisions are reviewed.
How to use the APACHE II Severity Score Calculator
- Enter Worst core temperature (°C).
- Enter Worst mean arterial pressure (mmHg).
- Enter Worst heart rate (beats/min).
- Enter Worst respiratory rate (breaths/min).
- Enter Oxygenation variable.
- Enter PaO₂ or A–aDO₂ value (mmHg).
- Enter Arterial pH (pH).
- Enter Serum sodium (mmol/L).
- Enter Serum potassium (mmol/L).
- Enter Serum creatinine (mg/dL).
- Enter Acute renal failure doubling rule.
- Enter Hematocrit (%).
- Enter White-cell count (×10³/µL).
- Enter Glasgow Coma Scale (points).
- Enter Age (years).
- Enter Qualifying chronic-health status.
- Choose Calculate and read the result panel.
- Use Download PDF or Download Word to save a result sheet.
Formula
APACHE II = acute physiology score + age points + chronic-health points. The acute physiology score adds temperature, MAP, heart rate, respiratory rate, oxygenation, pH, sodium, potassium, creatinine, hematocrit, white-cell count, and (15 − GCS) using the APACHE II bands.
This page implements the published APACHE II point bands and makes two branches explicit: use PaO₂ when FiO₂ is below 0.5 or A–aDO₂ when FiO₂ is at least 0.5, and double creatinine points only when the qualifying acute-renal-failure rule applies. It reports arithmetic, not prognosis or treatment.
Worked example
All entered values are in the zero-point bands, so APACHE II = 0 + 0 + 0 = 0 points.
Assumptions and limits
- Inputs represent the worst qualifying values in the specified assessment window, entered by trained clinical staff.
- Temperature is core temperature in degrees Celsius and blood pressure is entered as mean arterial pressure, not systolic pressure.
- The oxygenation mode is selected according to FiO₂ and the corresponding PaO₂ or A–aDO₂ value is entered in mmHg.
- Creatinine is entered in mg/dL and its APACHE point is doubled only when the acute renal failure rule is explicitly selected.
- GCS points are calculated as 15 minus the actual GCS, with GCS constrained to 3–15.
- Age and chronic-health points are added to the acute physiology score exactly as selected, with no mortality equation applied.
- The score is intended for trained ICU severity assessment and population-level comparison, not individual triage or treatment selection.
- Local protocols, source documentation, and qualified critical-care judgment take priority if they use a different version or handling rule.
Who uses this calculator?
- Critical-care students learning APACHE II arithmetic
- Clinicians checking a documented score against the published bands
- Researchers preparing a transparent severity-score worksheet
When is it useful?
- Separate acute physiology, age, and chronic-health contributions.
- Audit the PaO₂/A–aDO₂ branch and GCS subtraction.
- Reproduce a score from a documented set of worst values without applying a mortality claim.
Context and background
How health estimates should be read
Health calculators use measurements and population-level relationships to produce screening or planning estimates. They describe the supplied model; they do not diagnose, prescribe, or replace clinical judgment.
Many familiar health formulas began as practical ways to summarize measurements. Their limits matter as much as their output because individual bodies, medications, conditions, and professional standards vary.
Research and review
How this guide was researched
Researched by Hassan ALRowaie, Founder and editorial researcher at WorldCalculate.
This guide follows the live calculator's declared inputs, formula, worked example, assumptions, validation boundaries, and source-backed methodology. The review date describes editorial review of the calculator explanation; it is not a promise that external facts or rates remain current.
APACHE II is a structured ICU severity-of-illness score built from acute physiology, age, and chronic-health points. WorldCalculate exposes the component arithmetic while clearly limiting the page to calculation support for trained use.
What APACHE II is for
APACHE II summarizes selected physiologic abnormalities and background risk for critical-care assessment and research. It is designed to organize information, not to replace bedside judgment.
The score has three parts: an acute physiology score, age points, and chronic-health points. The calculator keeps those parts separate.
The 12 acute-physiology variables
The acute section uses temperature, mean arterial pressure, heart rate, respiratory rate, oxygenation, arterial pH, sodium, potassium, creatinine, hematocrit, white-cell count, and Glasgow Coma Scale points.
Each value is assigned points by a band. A normal-band value contributes zero; high or low abnormalities can contribute more points.
Oxygenation is a branch
When FiO₂ is below 0.5, the standard table uses PaO₂. When FiO₂ is at least 0.5, it uses the alveolar–arterial oxygen gradient, A–aDO₂.
The oxygenation selector prevents the two measurements from being silently mixed. Enter the corresponding documented value and keep its mode beside the result.
Creatinine and acute renal failure
Creatinine has its own point bands, and the APACHE II table allows the creatinine points to be doubled when the acute renal failure rule applies.
The calculator asks for that branch explicitly. It does not infer acute renal failure from the creatinine number, diagnosis, urine output, or a single laboratory result.
GCS and the age component
The neurologic contribution is 15 minus the actual Glasgow Coma Scale. A fully alert GCS of 15 therefore contributes zero points.
Age points are then added by bands: under 45, 45–54, 55–64, 65–74, and 75 or older. The score is not age-adjusted in any other way.
Chronic-health points
Qualifying severe organ insufficiency or immunocompromise can add points depending on whether the patient is nonoperative or emergency postoperative, or elective postoperative.
This field requires a documented clinical classification. The calculator does not decide whether a condition meets the score’s definition.
Why the total is not a prognosis
APACHE II was developed for severity classification and outcome modeling in populations. A total does not tell an individual patient what will happen, whether to intubate, or which treatment is appropriate.
Do not use an online total for emergency triage or to delay escalation. Clinical teams use current status, trends, diagnoses, treatment response, and local protocols.
FAQs
What is the maximum? The standard total is commonly described as 71. Should I use the best value? No; the method uses the worst qualifying values in its stated window. Can this calculate mortality? No; no mortality equation or patient-specific prediction is produced here.
Frequently asked questions
What is the APACHE II Severity Score Calculator?
Calculate the APACHE II arithmetic from 12 acute-physiology components, age points, and chronic-health points, with oxygenation mode and creatinine weighting made explicit.
What is the formula for the APACHE II Severity Score Calculator?
APACHE II = acute physiology score + age points + chronic-health points. The acute physiology score adds temperature, MAP, heart rate, respiratory rate, oxygenation, pH, sodium, potassium, creatinine, hematocrit, white-cell count, and (15 − GCS) using the APACHE II bands. This page implements the published APACHE II point bands and makes two branches explicit: use PaO₂ when FiO₂ is below 0.5 or A–aDO₂ when FiO₂ is at least 0.5, and double creatinine points only when the qualifying acute-renal-failure rule applies. It reports arithmetic, not prognosis or treatment.
What do I need to use this calculator?
Enter Worst core temperature, Worst mean arterial pressure, Worst heart rate, Worst respiratory rate, Oxygenation variable, PaO₂ or A–aDO₂ value, Arterial pH, Serum sodium, Serum potassium, Serum creatinine, Acute renal failure doubling rule, Hematocrit, White-cell count, Glasgow Coma Scale, Age, Qualifying chronic-health status, then choose Calculate.
What are the limits of this calculator?
Inputs represent the worst qualifying values in the specified assessment window, entered by trained clinical staff. Temperature is core temperature in degrees Celsius and blood pressure is entered as mean arterial pressure, not systolic pressure. The oxygenation mode is selected according to FiO₂ and the corresponding PaO₂ or A–aDO₂ value is entered in mmHg. Creatinine is entered in mg/dL and its APACHE point is doubled only when the acute renal failure rule is explicitly selected. GCS points are calculated as 15 minus the actual GCS, with GCS constrained to 3–15. Age and chronic-health points are added to the acute physiology score exactly as selected, with no mortality equation applied. The score is intended for trained ICU severity assessment and population-level comparison, not individual triage or treatment selection. Local protocols, source documentation, and qualified critical-care judgment take priority if they use a different version or handling rule.
Methodology
This calculator is part of the WorldCalculate library. Its formula, example, assumptions, input bounds, and output formatting follow the official methodology.
Use this calculator as part of a bigger plan
These WorldCalculate collections connect this tool with related questions while keeping each calculation separate and transparent.