HesapHanem

Shock Index Calculator

Find the shock index.

How it is calculated

SI = HR ÷ SBP, where HR is heart rate in beats per minute and SBP is systolic blood pressure in mmHg. The result is a plain ratio with no unit, shown to two decimals. The tool labels the result Elevated when the unrounded ratio is above 0.9 and Normal at 0.9 or below, so a value displayed as 0.90 can be labelled either way (90.4 / 100 shows 0.90 and Elevated). A systolic pressure of zero or less returns no result. The labels are a screening aid, not a diagnosis, and clinical cut-offs vary by setting and patient group.

Worked example

Heart rate 110 bpm, systolic pressure 90 mmHg. Divide: 110 ÷ 90 = 1.2222, rounded to 1.22. Because 1.22 is above 0.9, the status reads Elevated. For comparison, 70 bpm over 120 mmHg gives 0.58 and a Normal label.

Try this example →

Common mistakes

  • Entering diastolic instead of systolic pressure (the lower number of a reading such as 120/80); the ratio then comes out far too high.
  • Swapping the two fields, which gives the inverse ratio (SBP ÷ HR) of about 0.8 instead of about 1.2.
  • Typing the reading as one number such as 12080 or 120/80 instead of only the top value, 120.
  • Reading Normal as proof of safety: a ratio below the cut-off does not rule out shock, especially in people on heart-rate-lowering medicines.
  • Using a single reading taken during pain, stress or exertion; the heart rate then inflates the index.

Sources

About this calculator

This calculator finds the shock index — heart rate divided by systolic blood pressure — a simple bedside ratio that's normally around 0.5 to 0.7 in a healthy resting adult. A rising shock index can flag hemodynamic instability before blood pressure itself drops.

Emergency physicians, trauma teams and paramedics use it as a fast triage tool, particularly for hemorrhage and sepsis, because it can pick up early compensated shock — when heart rate climbs to maintain blood pressure — sooner than blood pressure alone would. It's a screening number, not a diagnosis on its own.

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  • Editorial team

    The tool applies a single cut-off of 0.9 to everyone. Age and heart-rate-lowering medicines change what is usual, so read the Elevated label as a prompt to look more closely and to speak to a clinician, not as an answer. Enter only the top number of the blood pressure. If you track readings over time, post what you kept the same, such as position and time of day.

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