About the SIRS Criteria Calculator
The systemic inflammatory response syndrome (SIRS) criteria were defined at the 1991 ACCP/SCCM Consensus Conference (Bone et al., Chest 1992). SIRS is present when at least two of four findings are met: temperature above 38 °C or below 36 °C; heart rate above 90 beats per minute; respiratory rate above 20 per minute or PaCO₂ below 32 mmHg; and a white blood cell count above 12,000/mm³, below 4,000/mm³, or more than 10% immature (band) forms.
This calculator checks each criterion, counts how many are met and shows which ones drove the result. It is aimed at clinicians, nurses and students who still meet SIRS in triage protocols, older sepsis literature and exams. Under the 1992 definitions, SIRS plus a confirmed or suspected infection was called sepsis.
The 2016 Sepsis-3 definitions replaced SIRS-based sepsis with organ dysfunction measured by SOFA, because SIRS is very sensitive but not specific — many patients with uncomplicated infection, trauma, pancreatitis or even exercise meet two criteria. The criteria apply to adults; children use age-specific thresholds.
With the default inputs, the sirs criteria met is 0 / 4. Change any value above to recalculate instantly.
How to use the sirs criteria calculator
- 1Choose °C or °F and enter the temperature.
- 2Enter heart rate and respiratory rate.
- 3Add PaCO₂ if a blood gas is available (otherwise leave 0).
- 4Enter the white cell count and tick bands > 10% if reported.
- 5Read how many criteria are met — 2 or more means SIRS criteria are satisfied.
Formula and method
Each of the four criteria counts once, whichever of its alternative thresholds is crossed (for example, either a respiratory rate above 20 or a PaCO₂ below 32 mmHg satisfies the respiratory criterion). The count runs from 0 to 4 and SIRS is present at 2 or more. Fahrenheit temperatures are converted with °C = (°F − 32) × 5/9 before comparison.
The thresholds are those of the 1991 ACCP/SCCM consensus conference, published in Chest and Critical Care Medicine in 1992. They are adult cut-offs and should be interpreted as a change from the patient’s baseline caused by an acute process.
- T
- Core temperature
- HR
- Heart rate, beats per minute
- RR
- Respiratory rate, breaths per minute
- WBC
- White blood cell count, ×10³ per µL
Worked examples
Normal observations
A temperature of 37 °C, heart rate 80, respiratory rate 16 and WBC 8 meet none of the criteria.
Febrile, tachycardic patient (in °F)
101.3 °F is 38.5 °C (> 38), heart rate 112 (> 90) and WBC 14.5 (> 12) meet three criteria. Respiratory rate 16 does not.
Hypothermia with low PaCO₂
35.4 °C is below 36 °C, and although the respiratory rate is 18, a PaCO₂ of 28 mmHg (< 32) satisfies the respiratory criterion — 2 of 4 met.
Frequently asked questions
How many SIRS criteria are needed?+
At least two of the four criteria must be met for SIRS. Under the 1992 definitions, SIRS caused by a confirmed or suspected infection was termed sepsis.
Is SIRS still used to define sepsis?+
Not in the current Sepsis-3 definitions (2016), which define sepsis as infection with an acute rise of 2 or more SOFA points. SIRS is still used in some screening protocols and quality measures because it is sensitive.
Why is SIRS considered non-specific?+
Many non-infectious conditions — trauma, burns, pancreatitis, surgery, anxiety, exercise — raise heart rate, breathing and white cell count. So meeting two criteria does not by itself mean infection or sepsis — the Sepsis-3 task force cited this poor specificity as a key reason for retiring SIRS from the sepsis definition.
Do the SIRS criteria apply to children?+
No. Children have different normal heart rates, breathing rates and white cell counts, so paediatric SIRS uses age-specific thresholds from the 2005 International Pediatric Sepsis Consensus.
What are bands?+
Bands are immature neutrophils reported on a manual blood film differential. More than 10% band forms (a left shift) meets the white cell criterion even when the total count is normal.
For healthcare professionals and education only. This calculator implements a published formula or score but is not a diagnosis and does not replace clinical judgment. Verify inputs and results against the original source before using them in patient care.