ABG Calculator & ABG Analyzer
Enter pH, PaCO₂, HCO₃⁻, and PaO₂ to interpret arterial blood gas results, then optionally calculate P/F ratio and assess ARDS criteria through a progressive oxygenation pathway.
Enter ABG values
Use pH, PaCO₂, HCO₃⁻, and PaO₂ values from the same arterial sample. Reference ranges are shown as entry hints.
Normal ABG values
Arterial blood gas reference ranges at a glance
These commonly used adult ranges provide an interpretation framework, but laboratory references and clinical context can vary.
Overall arterial acid–base direction
Respiratory contribution to acid–base balance
Metabolic contribution to acid–base balance
Arterial oxygen tension; context dependent
*PaO₂ is especially dependent on age, FiO₂, altitude, and the clinical setting.
Master blood gases. Make every ABG click.
Practice acid-base status, primary disorders, compensation, and oxygenation—then reinforce missed concepts with focused review.
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ABG interpretation workflow
How to use this ABG analyzer
Use this ABG calculator when you already have arterial blood gas values and want a fast, organized interpretation. Enter pH, PaCO₂, HCO₃⁻, and PaO₂, then review the likely acid-base pattern and oxygenation category together.
- Start with pH to decide whether the blood gas shows acidemia, alkalemia, or a normal-range pH.
- Compare PaCO₂ and HCO₃⁻ to determine whether the primary disorder is respiratory, metabolic, or mixed. When the pattern suggests metabolic acidosis, verify whether the PaCO₂ response is appropriate with Winter’s Formula instead of assuming every low PaCO₂ is a primary respiratory alkalosis.
- Use PaO₂ to classify oxygenation and decide whether hypoxemia is present.
- After the ABG result, optionally add FiO₂ to calculate P/F ratio. When the ratio falls within an ARDS oxygenation range, continue to the respiratory-support-aware Berlin or Global ARDS criteria assessment.
For deeper study, read the ABG Analysis Guide or practice repeated cases with the ABG interpretation quiz.
Related tools & guides
Keep building acid-base confidence
Acid–base interpretation with oxygenation kept in context
The ABG calculator evaluates arterial pH first, compares PaCO₂ and HCO₃⁻ to identify a likely primary acid–base process, checks whether the other value moves in a compensatory direction, and reports the PaO₂ band separately. Optional P/F and ARDS steps appear only after the initial result.
- Directional compensation is not presented as proof that compensation is quantitatively appropriate.
- PaO₂ is interpreted with an explicit reminder to consider FiO₂, age, altitude, and baseline physiology.
- P/F ratio is presented as an oxygenation range—not an ARDS diagnosis—until the remaining definition criteria are assessed.
- HFNC uses documented flow for the Global ARDS pathway; the analyzer never estimates mean airway pressure.
Common ABG questions
ABG calculator FAQ
Quick answers for students, respiratory therapists, nurses, and clinicians reviewing arterial blood gas interpretation.
What is an ABG calculator?
An ABG calculator organizes arterial pH, PaCO₂, HCO₃⁻, and PaO₂ values to identify a likely acid-base pattern, describe compensation direction, and place oxygenation in clinical context.
What is a normal ABG?
Normal ABG values are pH 7.35–7.45, PaCO₂ 35–45 mmHg, HCO₃⁻ 22–29 mEq/L, and PaO₂ 80–100 mmHg.
How do you interpret an ABG?
Start with pH, then compare PaCO₂ and HCO₃⁻ to identify the primary disorder, assess compensation, and finish by evaluating oxygenation.
What does PaO₂ indicate?
PaO₂ reflects arterial oxygenation and helps classify hypoxemia as mild, moderate, or severe.
What is compensation in ABGs?
Compensation is the body’s attempt to bring pH back toward normal through respiratory or metabolic adjustment.
Can this ABG analyzer calculate the P/F ratio?
Yes. After the initial ABG interpretation, enter the FiO₂ delivered at the same clinical moment. The analyzer carries forward PaO₂ and calculates the PaO₂/FiO₂ ratio without requiring mean airway pressure.
Does a low P/F ratio diagnose ARDS?
No. A P/F ratio of 300 or less falls within an ARDS oxygenation range, but ARDS assessment also requires timing, imaging, edema-origin, and respiratory-support criteria. The analyzer offers an optional Berlin or Global Definition pathway based on the support being used.