Injury Severity Score Calculator

Created by Joanna Michałowska, PhD candidate
Reviewed by Dominik Czernia, PhD candidate and Jack Bowater
Last updated: Feb 15, 2022

The Injury Severity Score calculator helps to assess trauma severity, especially in patients with multiple injuries. It helps to define the term "major trauma" and ISS correlates with mortality, morbidity, and hospitalization time after injury. Read the text below to find out more about the Injury Severity Score calculation (ISS score trauma) and interpretation.

If you are interested in calculators that assess the severity of other medical conditions, check out the revised trauma score, SOFA score and SAPS II calculators.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace professional medical advice.

Injury severity score

Baker and colleagues created the Injury Severity Score in 1974. This medical score is based on the previously developed Abbreviated Injury Scale (AIS) and takes into account the three (out of six) most severe system injuries.

This adjustment allows doctors to add increasing weight to the most severe injuries. According to the study's results, injuries that alone may not be life-threatening can significantly influence mortality when combined with other trauma.

Injury Severity Score calculation

In this paragraph, you will find information on how to calculate Injury Severity Score.

Trauma in the ISS score can be related to six regions of the human body:

  1. Head and neck (includes cervical spine);
  2. Face: facial skeleton, nose, mouth, eyes, and ears;
  3. Chest: thoracic spine and diaphragm;
  4. Abdomen: abdominal organs and lumbar spine (includes pelvic contents);
  5. Extremities or pelvic girdle: pelvic skeleton; and
  6. External

Each part of the body is then scored for the worst injury as follows:

No injury

After scoring each body system, we perform the injury severity score calculation according to the following rules:

  1. Choose the three most severely injured body systems.
  2. Perform Injury Severity Score calculation by adding the three highest squared scores :

ISS = highest1² + highest2² + highest3²

If any body system has a score of 6, ISS is automatically set to have the highest value - 75 points.

ISS score trauma interpretation

Now that you know how to calculate Injury Severity Score, let's take a look at its interpretation:

  • Injury Severity Score (ISS) takes values from 0 to 75 points;

  • ISS score is the only anatomical scoring system that correlates linearly with mortality, morbidity, hospitalization time, and other severity measures;

  • We associate ISS score > 15 with major trauma; and

  • Bolorunduro et al. proposed the following classification of the injuries:

less than 9
25 and more
Very severe/profound

Injury Severity Score calculator - a practical example

It would help you check you know how to calculate Injury Severity Score if we used a practical example of a patient who has been in a car crash. Doctors graded his injuries as follows:

Worst injury in the region
Head and neck
No injury (0 points)
Minor (1 points)
Moderate (2 points)
Serious (3 points)
No injury (0 points)
No injury (0 points)

First, we need to find the regions with the highest score. In this example, those are:

  1. Abdomen - 3 points
  2. Chest - 2 points
  3. Face - 1 point

Now we can calculate the patient's Injury Severity Score (ISS score trauma) as follows:

ISS = highest1² + highest2² + highest3²

ISS = 3² + 2² + 1²

ISS = 9 + 4 + 1²

ISS = 14

This patient's injuries can be categorized as moderate.

Joanna Michałowska, PhD candidate
Worst injury in the area:
Head and neck
No injury
No injury
No injury
No injury
No injury
No injury
Injury Severity Score
An Injury Severity Score of less than 9 can be classified as minor trauma.
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