Shock Index Calculator

The shock index is your heart rate in beats per minute divided by your systolic blood pressure in mmHg. For example, a heart rate of 110 and a systolic pressure of 100 gives a shock index of 1.10. It is a quick screening number that can hint at circulatory stress before the blood pressure itself falls.

In a resting adult the shock index usually sits between 0.5 and 0.7. Values from 0.7 to 0.9 are borderline, and a value at or above 0.9 is considered elevated. A shock index at or above 1.0 often points to significant hemodynamic instability and warrants urgent attention.

When circulation starts to fail, the heart speeds up before blood pressure drops, so a rising shock index can reveal occult hemorrhage or early shock that a single blood pressure reading might miss. In trauma and emergency care it helps flag patients who look stable but are not. It is one signal among many, not a diagnosis on its own.

The modified shock index divides heart rate by mean arterial pressure, where MAP equals (systolic plus two times diastolic) divided by three; a modified value above 1.3 suggests instability. The age-adjusted shock index multiplies age in years by the shock index and is used in trauma triage for older patients, where a value at or above 50 is linked to higher mortality. Enter a diastolic pressure or an age in this tool to see each variant.

Yes. Beta-blockers and pacemakers can hold the heart rate down even during blood loss, which masks a true rise in the shock index. Pregnancy, chronic hypertension, athletic conditioning, and pain or anxiety can also shift the number, so it should always be read alongside the full clinical picture.

No. This shock index calculator is for education and quick reference only and is not a substitute for professional medical advice, diagnosis, or treatment. If you are worried about someone's vital signs or a possible emergency, contact a clinician or emergency services right away.