Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Shock index
1.16
Age-adjusted shock index (age × SI)
52.1
Screening interpretation
High — reassess urgently
Psst — share this and help Rex grow
One click, a permanent link with your numbers baked in.
How to use this
- 1Enter heart rate (bpm).
- 2Enter systolic blood pressure (mmHg).
- 3Enter age (years).
- 4Read your shock index on the right — it updates as you type.
- 5Hit Share to keep the scenario or send it to someone.
About this calculator
Shock index is heart rate divided by systolic blood pressure, and it flags hemodynamic compromise earlier than either vital sign alone because compensatory tachycardia can mask a falling blood pressure in early shock, especially hemorrhagic shock in trauma and postpartum hemorrhage. A normal shock index is roughly 0.5 to 0.7; values at or above 0.9-1.0 correlate with higher transfusion needs, ICU admission, and mortality in trauma and sepsis literature. It is a rapid triage screen, not a diagnosis, and it performs worse in patients on beta-blockers (blunted tachycardic response) or with baseline hypertension (higher "normal" pressure masking relative hypotension). Age-adjusted and modified shock index (using mean arterial pressure instead of systolic) variants exist and can be more sensitive in elderly patients, where a shock index of even 0.7-0.8 may already represent significant compromise relative to their baseline. Use it to trigger closer monitoring or workup, not to rule out shock on a normal value alone. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.
Worked example
Using the values the calculator loads with:
Inputs
- Heart rate: 110 bpm
- Systolic blood pressure: 95 mmHg
- Age: 45 years
Results
- Shock index: 1.16
- Age-adjusted shock index (age × SI): 52.1
- Screening interpretation: High — reassess urgently
What each field means
Inputs
- Heart rate (bpm)
- The heart rate used in the calculation, measured in bpm. Starts at 110 bpm so you have a working example on load. Accepted range: 20–220 bpm.
- Systolic blood pressure (mmHg)
- The systolic blood pressure used in the calculation, measured in mmHg. Starts at 95 mmHg so you have a working example on load. Accepted range: 40–250 mmHg.
- Age (years)
- The age used in the calculation, measured in years. Starts at 45 years so you have a working example on load. Accepted range: 1–110 years.
Results
- Shock index
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Age-adjusted shock index (age × SI)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Screening interpretation
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What shock index warrants action?
A shock index at or above 0.9-1.0 has repeatedly been associated with higher transfusion requirements and mortality in trauma and obstetric hemorrhage studies. Treat that threshold as a trigger for reassessment, additional access, labs, and closer monitoring rather than waiting for overt hypotension to develop.
Why does it work better than blood pressure alone?
Young, otherwise healthy patients compensate for blood loss with vasoconstriction and tachycardia, which can keep systolic blood pressure deceptively normal until 30% or more of blood volume is lost. Because shock index incorporates heart rate, it captures that compensatory tachycardia and flags trouble sooner.
Does it work in elderly or beta-blocked patients?
Less reliably. Beta-blockers blunt the tachycardic response, so a beta-blocked patient in shock may show a falsely reassuring shock index. In elderly patients, age-adjusted shock index (age × SI) has better predictive performance because it accounts for reduced physiologic reserve at any given index value.
Can shock index be used in sepsis, not just trauma?
Yes, it has been studied in sepsis and postpartum hemorrhage as well, generally with the same threshold logic: rising or elevated shock index correlates with worse outcomes and should prompt fluid resuscitation review, lactate measurement, and closer hemodynamic monitoring.
Accuracy and limitations
- Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
- Results do not account for medical conditions, medication, or pregnancy.
- Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.
Related tools
QTc Calculator (Bazett & Fridericia)
Correct the QT interval for heart rate using two standard formulas.
CURB-65 Pneumonia Severity Score
Estimate 30-day mortality risk in community-acquired pneumonia.
Glasgow Coma Scale (GCS) Calculator
Standardize level of consciousness across eye, verbal, and motor response.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Shock Index Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/shock-index
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/shock-index" target="_blank" rel="noopener">Shock Index Calculator — RevenueLab</a> (2026).</p>
Source: [Shock Index Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/shock-index) (2026).