Glasgow Coma Scale Calculator

The Glasgow Coma Scale was developed in 1974 at the University of Glasgow by Graham Teasdale and Bryan Jennett. It became one of the most widely used tools in emergency and intensive care medicine because it is fast, reproducible, and does not require special equipment.

The scale has three components: Eye opening (E, 1-4), Verbal response (V, 1-5), and Motor response (M, 1-6). The total GCS score is E + V + M, ranging from 3 (deepest coma) to 15 (fully awake and oriented).

Standard severity classification for traumatic brain injury: Mild TBI: GCS 13-15. The patient is conscious and conversational. This includes most concussions. Moderate TBI: GCS 9-12. The patient can be roused but is not fully oriented. Severe TBI: GCS 3-8. The patient cannot follow commands, open eyes spontaneously, or speak meaningful words. A score of 8 or below defines coma.

The motor score carries the most prognostic weight. An M score of 1 or 2 indicates severe brainstem dysfunction. Decorticate posturing (M3) involves flexion of the arms toward the body; decerebrate posturing (M2) involves extension of all extremities, suggesting damage lower in the brainstem.

The GCS has limitations. It cannot be fully applied to patients who are intubated, sedated, or who have pre-existing conditions affecting baseline neurological function. For an intubated patient the verbal component is untestable and is recorded as VT rather than guessed at, and the total is written with a T suffix: E3 VT M5 is reported as 8T, not as 8. The two are not the same number. A maximum of 10T is achievable where a normal patient could reach 15, so a T-score cannot be dropped into the 3-8 / 9-12 / 13-15 severity bands. Select VT in the verbal list and the calculator will report it that way.

Serial GCS scores matter more than a single reading. A patient falling from GCS 14 to GCS 10 over an hour is a clinical emergency regardless of the absolute number.

Score the best response, not the average. If the left arm localises and the right one only withdraws, the motor score is 5. Asymmetry is clinically important and gets documented separately, but it does not lower the number. Similarly, record the best eye opening seen during the assessment rather than the response at one moment.

A note on the low end: 3 is the floor, not zero. Each component starts at 1, so a patient with no response at all scores 3. There is no such thing as a GCS of 0, and a reported score below 3 is an arithmetic error.