Injury Severity Score Calculator

Score AIS severity (0-6) for six body regions to compute the Injury Severity Score, the trauma-triage standard equal to the sum of squares of the three most severely injured regions.

Quick Facts

Score range
0 to 75 points
Sum of the squares of the three highest AIS scores from three different body regions; any AIS of 6 sets ISS to 75.
Body regions
6 regions scored
Head/neck, face, chest, abdomen/pelvic contents, extremities/pelvic girdle, external - the single worst AIS per region counts.

Your Results

Calculated
Injury Severity Score
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Sum of three worst regions squared (0-75)
Three highest AIS scores
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Values used in the calculation
Regions injured
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Out of 6 body regions
Severity category
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Common ISS classification band

Ready

Select the worst AIS severity (0-6) for each body region, then calculate the Injury Severity Score.

About the Injury Severity Score

The Injury Severity Score (ISS) is an anatomical trauma severity score first described by Baker, O'Neill, Haddon, and Long in 1974. It summarizes a patient's total injury burden across the body from injuries already graded on the Abbreviated Injury Scale (AIS), the coding system used to rate the severity of each individual injury.

How the score is built

The body is divided into six regions: head or neck, face, chest, abdomen or pelvic contents, extremities or pelvic girdle, and external (skin). Each region is assigned a single AIS severity score from 0 (no injury) to 6 (unsurvivable), using the worst injury recorded in that region. The Injury Severity Score is the sum of the squares of the three highest AIS scores, taken from three different regions:

ISS = A² + B² + C²

...where A, B, and C are the AIS scores of the three most severely injured body regions. If any single region scores an AIS of 6, the injury is classified unsurvivable and the ISS is automatically set to the maximum value of 75, regardless of the other five regions.

Interpreting the result

ISS ranges from 0 (no recorded injury) to 75. Trauma registries commonly group scores into approximate bands - roughly 1 to 8 as minor, 9 to 15 as moderate, 16 to 24 as serious, and 25 to 75 as severe - and an ISS above 15 is widely used as the threshold for "major trauma" in audits and research. These bands describe patterns across trauma populations, not a forecast for any one patient.

When to consult a professional

This tool performs the standard ISS arithmetic for education, triage documentation, and research use. It is not a diagnosis and does not replace clinical judgment. Coding individual injuries on the AIS and any treatment decisions should be handled by trained trauma clinicians or certified AIS coders.

Frequently Asked Questions

What is the Injury Severity Score (ISS)?
The Injury Severity Score is an anatomical trauma severity score. It grades injuries in six body regions on the Abbreviated Injury Scale (AIS) from 0 to 6, then combines the three worst regions into a single number from 0 to 75. Higher scores mean more severe, more widespread injury.
How is the ISS calculated?
Assign one AIS severity score (0-6) to each of six body regions: head or neck, face, chest, abdomen or pelvic contents, extremities or pelvic girdle, and external. Take the three highest AIS scores from three different regions and add their squares: ISS = A-squared + B-squared + C-squared. If any region scores an AIS of 6, the ISS is automatically set to 75.
What ISS values indicate major trauma?
Many trauma registries use approximate bands of 1-8 as minor, 9-15 as moderate, 16-24 as serious, and 25-75 as severe, with an ISS above 15 commonly used as the threshold for major trauma. These bands describe patterns in trauma audit data, not an individual patient's outcome, and injury coding and treatment decisions should involve trained trauma clinicians.

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