Injury Severity Score (ISS) Calculator
Enter the highest AIS (Abbreviated Injury Scale) value for each body region. Use whole numbers from 0 to 6.
0 = no injury, 1 = minor, 2 = moderate, 3 = serious, 4 = severe, 5 = critical, 6 = maximal/unsurvivable.
What is an ISS calculator?
An ISS calculator estimates trauma severity using the Injury Severity Score (ISS), a widely used metric in emergency medicine and trauma research. It takes injury data from six body regions and converts it into a single number from 0 to 75.
Clinicians, trauma registries, and researchers use ISS to help classify injury burden, compare patient populations, and evaluate outcomes. It is not a standalone treatment decision tool, but it is very useful for consistent communication.
How ISS is calculated
Step-by-step formula
- Record the highest AIS score in each of the six body regions.
- Select the three highest AIS values across different regions.
- Square each of those three values and add them together.
- If any AIS value is 6, ISS is automatically set to 75.
Formula: ISS = A² + B² + C², where A, B, and C are the top three regional AIS scores.
Body regions used in ISS
- Head/Neck
- Face
- Chest
- Abdomen/Pelvic Contents
- Extremities/Pelvic Girdle
- External
How to interpret ISS scores
A practical interpretation commonly used in education and triage discussions is:
- 1–8: Mild trauma burden
- 9–15: Moderate trauma burden
- 16–24: Severe trauma (major trauma threshold often begins at 16)
- 25–49: Very severe trauma
- 50–74: Critical trauma burden
- 75: Maximal score (includes any AIS 6 injury)
Example calculation
Suppose the highest regional AIS values are: Head/Neck 4, Chest 3, Abdomen 2, and all others 0. The top three are 4, 3, and 2.
ISS = 4² + 3² + 2² = 16 + 9 + 4 = 29.
Important limitations
- ISS summarizes anatomical injury, but does not directly include physiology (e.g., blood pressure, oxygenation).
- Timing and quality of treatment still strongly influence outcomes.
- Different patients with the same ISS can have different prognoses.
- This calculator is educational and should not replace clinical judgment.
FAQ
Is ISS the same as AIS?
No. AIS is a score for a specific injury in a body region. ISS combines regional AIS values into one overall severity score.
Why does AIS 6 make ISS equal 75?
By definition of the scoring system, any maximal injury (AIS 6) automatically sets ISS to the highest possible value.
Can ISS be used alone to predict survival?
Not reliably by itself. It should be interpreted with age, physiology, comorbidities, mechanism of injury, and response to care.