PSI Calculator

Written by Great Medico

Updated September 24, 2026 •2 min read

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A lung or oxygenation value can be easy to misread when the formula is hidden. PSI Calculator makes the calculation explicit, so you can see what the result represents—and what it does not.

What this calculator does

PSI Calculator uses Sex, Patient age, Nursing-home resident, Neoplastic disease, Liver disease, Congestive heart failure, and the remaining displayed fields to produce the psi risk class ii used by this calculator. It only uses the fields shown in this calculator; it does not silently add tests, diagnoses, symptoms, or clinical variables that are absent from the interface. Implements the Pneumonia Severity Index (PORT) point score and risk classes for adults with community-acquired pneumonia.

How to use it

Enter or select Sex, Patient age, Nursing-home resident, Neoplastic disease, Liver disease, and the remaining displayed fields. Use measurements from the same respiratory assessment and confirm whether oxygen values are percentages, fractions, or pressures. If an input is unknown, it is better to leave the calculation unresolved than to invent a value.

How the calculation works

The Pneumonia Severity Index first checks the original low-risk Class I screening branch. If that is not met, it starts with an age/sex base and adds weighted points for nursing-home status, selected comorbidities, mental status, vital signs, arterial pH, BUN, sodium, glucose, hematocrit, oxygenation, and pleural effusion, then maps the total to risk class.

Example

Using the calculator’s prefilled demonstration values, the primary output is 65 points, labeled “PSI Risk Class II”; Approx. 30-day mortality is ~0.6% and Age/sex base is 65. That sample is useful for checking the calculation path, but real interpretation should use verified measurements from the same clinical or study context.

How to interpret the result

Read psi risk class ii in the context of the pulmonary measurement or scoring system used. Trends, measurement quality, oxygen/ventilator settings, and the disease being evaluated usually matter more than an isolated decimal value.

Limitations and notes

PSI was developed for adults with community-acquired pneumonia. It does not replace clinical judgment about hypoxemia, sepsis, inability to take oral therapy, social factors, rapidly worsening disease, or another diagnosis; disposition decisions can differ even within the same score class.