Shock Index Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/6/2026
The shock index is calculated by dividing heart rate by systolic blood pressure. For a heart rate of 80 bpm and a systolic pressure of 120 mmHg, the shock index is 0.67, within the normal range (0.5 to 0.7).
Explanation
The shock index is a rapid screening tool used in emergency medicine and critical care to detect early signs of shock, particularly hemorrhagic or hypovolemic shock. Its value comes from combining two vital signs into a single number: an elevated heart rate (compensatory tachycardia) can appear before any measurable drop in systolic blood pressure, something neither heart rate nor blood pressure alone detects as early. A normal index generally falls between 0.5 and 0.7 in a resting adult; an index of 0.9 or higher is associated, in several studies, with an increased risk of complications and mortality in critically ill or trauma patients, and is notably used to anticipate a need for transfusion. This indicator complements our resting heart rate calculator and blood pressure calculator classification: all three are used together by healthcare professionals, never in isolation, to assess a patient's hemodynamic status.
Example for a heart rate of 80 bpm and a systolic pressure of 120 mmHg
Inputs
Heart rate: 80 bpm. Systolic blood pressure: 120 mmHg.
Calculation
Shock index = 80 ÷ 120 = 0.67.
Result
The shock index is 0.67, within the normal range (0.5 to 0.7) for a resting adult.
Frequently asked questions
What is a normal shock index value?
In a healthy resting adult, the shock index generally falls between 0.5 and 0.7. A value in that range doesn't indicate any particular hemodynamic abnormality.
At what threshold does the shock index become concerning?
A shock index of 0.9 or higher is generally considered concerning and associated with an increased risk of complications in a critically ill or trauma patient. Some studies use a threshold of 1 as a sharper warning signal.
Does this index replace urgent medical advice?
No, absolutely not. The shock index is a screening tool used by trained healthcare professionals, alongside a full clinical exam — never a self-diagnosis tool. If you experience signs of distress, significant bleeding, or feeling unwell, contact emergency services immediately.