Trauma scoring
Injury Severity Score (ISS)
Enter the Abbreviated Injury Scale (AIS) value for each body region. The calculator squares the three highest scores from different regions and sums them to produce the ISS.
Assign the highest AIS injury within the region. AIS 6 automatically yields ISS 75.
Assign the highest AIS injury within the region. AIS 6 automatically yields ISS 75.
Assign the highest AIS injury within the region. AIS 6 automatically yields ISS 75.
Assign the highest AIS injury within the region. AIS 6 automatically yields ISS 75.
Assign the highest AIS injury within the region. AIS 6 automatically yields ISS 75.
Assign the highest AIS injury within the region. AIS 6 automatically yields ISS 75.
Top three AIS values²
- No injuries selected
Total ISS
0
Range 0–75
ISS ≤ 8 corresponds to minor injuries with low mortality risk.
Transfer to a Level I trauma center is recommended for ISS ≥ 16, according to many trauma systems.
How to Use This Calculator
Determine AIS per region
Use a certified AIS coder or trauma registrar to assign the highest AIS level in each body region.
Enter AIS values into the tool
Select the appropriate AIS (0–6). AIS 6 in any region automatically sets ISS to 75.
Review the ISS band
Use ISS together with physiologic scores (e.g., RTS, GCS) to triage and benchmark outcomes.
Formula
ISS = a² + b² + c²
- a, b, c are the three highest AIS scores from different body regions.
- If any AIS = 6, ISS is automatically 75 (maximum value).
- ISS ranges from 0 to 75; higher scores indicate greater injury burden and mortality risk.
Full Description
The Injury Severity Score (ISS) is an anatomical scoring system derived from the Abbreviated Injury Scale. It predicts mortality, morbidity, and hospital stay for trauma patients. By summing the squared AIS scores of the most severely injured body regions, ISS reflects the overall injury burden while ensuring injuries from different regions are considered.
ISS is widely used for trauma system benchmarking, research, and triage criteria. However, it depends on accurate AIS coding and may underestimate multiple injuries in the same region. Updated scoring systems like the New ISS (NISS) and Trauma and Injury Severity Score (TRISS) complement ISS for more nuanced risk prediction.
Frequently Asked Questions
What if a patient has multiple injuries in one region?
Select the single highest AIS score for that region; lesser injuries do not increase the ISS calculation.
How is ISS different from NISS?
NISS uses the three highest AIS scores regardless of region, potentially capturing multiple severe injuries in the same region.
Can ISS be used in prehospital triage?
Not directly, because AIS coding requires definitive diagnoses. ISS is best for retrospective analysis and quality improvement.
Does an ISS of 75 always mean death?
No. While originally deemed unsurvivable, improvements in trauma care mean some patients with ISS 75 survive. Use ISS alongside clinical judgement.