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Winters' Formula Calculator

Estimate the expected pCO₂ range in metabolic acidosis (with respiratory compensation).

HCO₃⁻ (Bicarbonate) Concentration (mmol/L):

Winters' Formula Calculator Overview

Winters' Formula Calculator is a clinical tool used to assess the expected respiratory compensation in patients with metabolic acidosis (e.g., diabetic ketoacidosis). It estimates the expected partial pressure of carbon dioxide (pCO₂) to determine if the body is compensating appropriately.

Why is Winters' Formula Used?

Detect inadequate compensation: Indicates possible respiratory acidosis.
Detect overcompensation: Suggests respiratory alkalosis or mixed acid-base disorder.
Evaluate patient stability: Helps guide further treatment or diagnostic decisions.

How to Use the Calculator

To calculate the expected pCO₂ range, simply enter:

Bicarbonate (HCO₃⁻) concentration: In mmol/L (mEq/L). Normal: 22–26 mmol/L.

HCO₃⁻ (Bicarbonate) is an essential buffer that helps regulate the body’s acid-base balance. It is measured in mmol/L through a blood test, usually from arterial or venous blood.

The result will provide an estimated pCO₂ range in mmHg (default) or kPa, depending on your selection.

Parameter Breakdown

Parameter	Symbol	Normal Range	Units	Description
Bicarbonate	HCO₃⁻	22–26	mmol/L	Buffer that resists pH changes in blood.
Carbon Dioxide (Partial Pressure)	pCO₂	35–45	mmHg	Reflects respiratory function and acid load.
Hydrogen Ion Concentration	[H⁺]	35–45	nmol/L	Determines blood acidity (pH).
Blood pH	pH	7.35–7.45	-	Measures overall acid-base status.

Interpretation

pCO₂ higher than expected: Indicates respiratory acidosis or mixed disorder.
pCO₂ lower than expected: Suggests respiratory alkalosis or mixed disorder.
pCO₂ within expected range: Indicates appropriate compensation.

Background Physiology

The body maintains acid-base balance using buffers (mainly the bicarbonate buffer system), lungs, and kidneys. Disruptions lead to metabolic or respiratory acidosis/alkalosis.

Disorder	Key Change	Effect on [H⁺]	Effect on pH
Respiratory Acidosis	↑ pCO₂	↑ [H⁺]	↓ pH
Metabolic Acidosis	↓ HCO₃⁻	↑ [H⁺]	↓ pH
Respiratory Alkalosis	↓ pCO₂	↓ [H⁺]	↑ pH
Metabolic Alkalosis	↑ HCO₃⁻	↓ [H⁺]	↑ pH

Additional Notes

Important: This formula is only applicable in metabolic acidosis with normal respiratory physiology.

Mixed Disorders: Suspect when values fall outside the expected range.

Use Alongside: Blood pH, anion gap, and clinical history for full interpretation.

Disclaimer

This tool provides clinical estimates only. It is not a replacement for professional medical judgment or a complete acid-base analysis.