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Shock Index Calculator

Work out shock index instantly with clear inputs, formula shown and shareable results.

About Shock Index Calculator

Divides heart rate by systolic pressure to give the shock index, and by mean arterial pressure for the modified index.

Formula

Shock index

SI = heart rate / systolic BP; modified SI = heart rate / mean arterial pressure; normal SI is about 0.5 to 0.7

Worked example

With the default values below, Shock Index Calculator returns Shock index of 1.100. Change any input above and every figure here is recalculated in your browser.

Inputs used

Heart rateaccepts 20–220 bpm
110 bpm
Systolic pressureaccepts 40–250 mmHg
100 mmHg
Diastolic pressureaccepts 20–160 mmHg
65 mmHg

Results

Shock index
1.100
Modified shock index
1.435
Interpretation
Raised (>=0.9) — suggests haemodynamic compromise

Step by step

  1. 1Values used
  2. 2Shock index
  3. 3Shock index= 1.100
  4. 4Modified shock index= 1.435
  5. 5Interpretation= Raised (>=0.9) — suggests haemodynamic compromise

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why is the shock index useful?

It rises before blood pressure falls, so it can flag occult hypoperfusion earlier than systolic pressure alone.

Does it apply in pregnancy?

Obstetric haemorrhage work uses higher thresholds, commonly 0.9 to 1.7, because baseline physiology differs.

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