Acid-Base (ABG) Calculator

Health

This acid-base calculator classifies an arterial blood gas (ABG) as acidemia, alkalemia or normal based on blood pH. Enter the pH, along with pCO2 and bicarbonate (HCO3-) for context, and it flags whether the blood is too acidic, too alkaline or within the normal 7.35-7.45 range. The pCO2 and HCO3- values help you reason about whether the cause is respiratory or metabolic.

Formula

pH 7.35-7.45 = Normal
  • Normal arterial blood pH is 7.35 to 7.45; below 7.35 is acidemia and above 7.45 is alkalemia.
  • pCO2 (normal ~35-45 mmHg) reflects the respiratory component of acid-base balance.
  • HCO3- (normal ~22-26 mEq/L) reflects the metabolic component.
  • A low pH with high pCO2 suggests respiratory acidosis; a low pH with low HCO3- suggests metabolic acidosis.
  • This is an educational screening aid, not a substitute for clinical interpretation of a full blood gas.

Example Calculation

Inputs
  • pH: 7.4
  • pCO2 (mmHg): 40
  • HCO3- (mEq/L): 24

A pH of 7.40, with pCO2 of 40 mmHg and HCO3- of 24 mEq/L, sits squarely in the normal range — the blood is neither acidemic nor alkalemic.

Frequently asked questions

What is acidemia versus alkalemia?
Acidemia is blood pH below 7.35 (too acidic); alkalemia is pH above 7.45 (too alkaline). Between them is the normal range.
Why enter pCO2 and HCO3-?
They help you tell whether a disturbance is respiratory (driven by pCO2) or metabolic (driven by bicarbonate), even though the status flag here is based on pH.
What is a normal arterial pH?
Roughly 7.35 to 7.45. Values outside this band indicate an acid-base disturbance that needs interpretation in context.
Does this diagnose the cause?
No. It classifies the pH. Identifying the specific disorder requires the full blood gas, compensation checks and the clinical picture.
Is this a clinical tool?
It is for education and quick reference only. Real blood gas interpretation should be done by a qualified clinician.