What is the shock index?
Enter a heart rate and a systolic blood pressure to see the shock index and where it sits against the ranges a published review gives. For information only. This is not medical advice or a diagnosis. Do not use it to make treatment decisions without a clinician. No licensed clinician has reviewed this page.
- Shock index
- 0.67
A heart rate of 80 beats per minute and a systolic pressure of 120 mmHg give a shock index of 0.67.
0.5 to 0.7 (normal range)
- Under 0.5
- 0.5 to 0.7 (normal range)
- Over 0.7, up to 1.0
- Over 1.0
- Range
- 0.5 to 0.7 (normal range)
Shock index: 0.67. A heart rate of 80 beats per minute and a systolic pressure of 120 mmHg give a shock index of 0.67.
Shock index
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
Divides the heart rate by the systolic blood pressure to give the shock index, and shows where it sits against the 0.5 to 0.7 normal range and the 1.0 mark.
Example with the default inputs (Heart rate (beats per minute) 80, Systolic, top number (mmHg) 120): A heart rate of 80 beats per minute and a systolic pressure of 120 mmHg give a shock index of 0.67.
Method: Shock index = heart rate (beats per minute) ÷ systolic blood pressure (mmHg), rounded once to 2 decimals, halves up; the range reads the rounded value.
- The heart rate and the systolic pressure are taken at the same time.
- The 0.5 to 0.7 normal range and the 1.0 mark are for adults (Koch 2019); children have their own age-based marks.
- The index is worked from the exact typed values and rounded once to 2 decimals, halves up; the range reads the rounded value.
Worked examples
Each example is checked against the calculator on every build.
- Heart rate (beats per minute) 80, Systolic, top number (mmHg) 120 gives Shock index 0.67, Range 0.5 to 0.7 (normal range).Source: Koch 2019: SI = HR ÷ SBP
- Heart rate (beats per minute) 120, Systolic, top number (mmHg) 100 gives Shock index 1.20, Range Over 1.0.Source: Koch 2019: 120 ÷ 100 = 1.20, over 1.0
- Heart rate (beats per minute) 100, Systolic, top number (mmHg) 100 gives Shock index 1.00, Range Over 0.7, up to 1.0.Source: Band edge: 100 ÷ 100 = 1.00 is not over 1.0 (Koch 2019)
- Heart rate (beats per minute) 105, Systolic, top number (mmHg) 150 gives Shock index 0.70, Range 0.5 to 0.7 (normal range).Source: Band edge: 105 ÷ 150 = 0.70, the top of the 0.5 to 0.7 range (Koch 2019) ()
- Heart rate (beats per minute) 141, Systolic, top number (mmHg) 200 gives Shock index 0.71, Range Over 0.7, up to 1.0.
- Heart rate (beats per minute) 50, Systolic, top number (mmHg) 125 gives Shock index 0.40, Range Under 0.5.
Medical disclaimer
This calculator is for information and education only. It is not medical advice, and its result is not a diagnosis. Do not use it to start, stop, or change a treatment without a clinician who knows your health history. No licensed clinician has reviewed this page. This site's editors checked the formulas and worked examples against published sources. If you think you have a medical emergency, call your local emergency number.
When this does not apply. The ranges come from a review of studies of adults seen in emergency departments, for trauma, bleeding, sepsis, heart attack, pulmonary embolism, and ectopic pregnancy (Koch 2019). The studies used different cut-offs, so the ranges are a guide, not a test. They do not apply to children, who have their own age-based marks. Drugs such as beta-blockers, a high baseline blood pressure, older age, and fever can all change the index. The review says the shock index should never be used on its own to diagnose or rule out a critical illness. Heart rates outside 20 to 300 beats per minute or systolic pressures outside 50 to 300 mmHg give no answer.
How it works
With the heart rate HR in beats per minute and the systolic blood pressure SBP in mmHg:
shock index SI = HR ÷ SBP
The page works with the exact typed values, rounds the index once to 2 decimals (halves up), and shows it. The range reads the rounded value:
| Shock index shown | Range on this page | Source |
|---|---|---|
| under 0.50 | Under 0.5 | below the normal range (Koch 2019) |
| 0.50 to 0.70 | 0.5 to 0.7 (normal range) | "currently accepted" normal range (Koch 2019, introduction) |
| 0.71 to 1.00 | Over 0.7, up to 1.0 | over 0.7 went with more admissions and deaths in the studies reviewed (Koch 2019, table 2) |
| 1.01 or more | Over 1.0 | above 1.0 widely linked to higher mortality (Koch 2019, abstract) |
The range text on the page is exactly one of: "Under 0.5", "0.5 to 0.7 (normal range)", "Over 0.7, up to 1.0", "Over 1.0".
Allowed input. Heart rate 20 to 300 beats per minute; systolic pressure 50 to 300 mmHg (the same bounds as the pulse pressure and mean arterial pressure pages). Decimals are allowed.
Assumptions
- The heart rate and the systolic pressure are taken at the same time, with the systolic pressure from an arm cuff reading.
- The ranges are for adults. The page does not work out the modified, age, or pediatric shock index.
- The results are for education. They are not medical advice.
Worked examples by hand
80 beats per minute, 120 mmHg (the page default). 80 ÷ 120 = 0.6667, shown as 0.67: 0.5 to 0.7 (normal range).
120 beats per minute, 100 mmHg. 120 ÷ 100 = 1.20: over 1.0.
100 beats per minute, 100 mmHg. 100 ÷ 100 = 1.00. That is not above 1.0, so the range is "Over 0.7, up to 1.0".
105 beats per minute, 150 mmHg. 105 ÷ 150 = 0.70, the top of the 0.5 to 0.7 range.
141 beats per minute, 200 mmHg. 141 ÷ 200 = 0.705, an exact half, shown as 0.71 (halves up). The range reads the shown value: over 0.7, up to 1.0.
50 beats per minute, 125 mmHg. 50 ÷ 125 = 0.40: under 0.5.
Other questions people ask
What is the shock index?
The heart rate divided by the systolic (top) blood pressure. It has no unit. A review by Koch and colleagues (2019) explains why it is used: early in shock, the heart rate and the blood pressure can each still look normal, while their ratio has already moved.
How do I calculate the shock index?
Divide the pulse in beats per minute by the systolic pressure in mmHg. A pulse of 80 with a blood pressure of 120/80 gives 80 ÷ 120 = 0.67. A pulse of 120 with a systolic pressure of 100 gives 120 ÷ 100 = 1.20.
What is a normal shock index?
Koch 2019 gives 0.5 to 0.7 as the currently accepted normal range for adults, and notes some evidence for values up to 0.9.
What does a shock index over 1.0 mean?
Koch 2019 reports that a shock index above 1.0 has been widely found to go with a higher risk of death and with other signs of serious illness, such as a need for massive transfusion or intensive care. The review also says the index should never be used on its own to diagnose or rule out a critical illness.
What is the modified shock index?
The heart rate divided by the mean arterial pressure (MAP) in place of the systolic pressure. Koch 2019 describes it, and an age shock index (age × shock index) for older adults. This page works out the standard shock index only; the mean arterial pressure calculator on this site gives the MAP.
Does the shock index work for children?
Not with the adult ranges. Children have a faster normal heart rate and a lower blood pressure, so Koch 2019 describes a separate pediatric age-adjusted shock index with its own marks for each age group. The ranges on this page are for adults.
What can make the shock index misleading?
Koch 2019 names drugs that change the heart rate or the blood pressure, such as beta-blockers, and notes doubts about the index in older adults, people with a fever, and people with long-term conditions. High blood pressure at baseline also changes it.