Winter’s Formula Calculator

Winter’s Formula Calculator — Expected pCO2 in Metabolic Acidosis

Calculate the expected pCO₂ in metabolic acidosis using Winter’s Formula. Essential tool for medical professionals assessing acid-base disorders and respiratory compensation.

Step 1: Patient Details

Serum Bicarbonate (HCO₃⁻) Level (mEq/L)

12.0

Actual Measured pCO₂ (mmHg) – Optional

40.0

Arterial pH – Optional

7.35

Winter’s Formula Explained

Winter’s Formula: Expected pCO₂ = (1.5 × [HCO₃⁻]) + 8 ± 2. Used to assess respiratory compensation in metabolic acidosis. If actual pCO₂ is within the expected range, respiratory compensation is appropriate.

Step 2: Calculation Options

Winter’s Formula Variant

Expected Compensation Type

Show clinical interpretation

Show compensation chart

Show clinical examples

Clinical Application

Winter’s Formula helps differentiate between simple metabolic acidosis and mixed acid-base disorders. If measured pCO₂ is higher than expected, consider respiratory acidosis. If lower, consider respiratory alkalosis.

Winter’s Formula Results

Summary

Clinical Interpretation

Compensation Analysis

Expected pCO₂ Range (Winter’s Formula)

26 ± 2 mmHg

Based on HCO₃⁻ = 12 mEq/L using Winter’s Formula

Calculated Formula

1.5×12 + 8

Expected Range

24-28 mmHg

Actual pCO₂

40.0 mmHg

Compensation Status

Inadequate

Clinical Interpretation

Analysis: The patient’s actual pCO₂ (40.0 mmHg) is above the expected range of 24-28 mmHg calculated using Winter’s Formula.

Interpretation: This suggests inadequate respiratory compensation for the metabolic acidosis. The higher-than-expected pCO₂ indicates a possible concurrent respiratory acidosis or insufficient respiratory response.

Clinical Considerations:

Evaluate for causes of impaired ventilation (COPD, asthma, drug overdose)
Assess respiratory rate and effort
Consider arterial blood gas for complete acid-base analysis
Review medications that might suppress respiratory drive

Next Steps: Further evaluation of respiratory function and consideration of mixed acid-base disorder is warranted.

Common Clinical Scenarios

Condition	Typical HCO₃⁻	Expected pCO₂	Compensation

Acid-Base Compensation Analysis

Winter’s Formula Calculation

Expected pCO₂ = (1.5 × [HCO₃⁻]) + 8 ± 2 mmHg

This formula estimates the appropriate respiratory compensation for metabolic acidosis. The normal compensatory response lowers pCO₂ by approximately 1.25 mmHg for each 1 mEq/L decrease in HCO₃⁻.

ΔpCO₂ / ΔHCO₃⁻ Ratio

1.25

Expected pH (7.4 base)

7.28

Anion Gap – Optional

–

Delta Ratio – Optional

–

Important Medical Disclaimer

This calculator is for educational purposes only. Always consult with a qualified healthcare professional for medical advice, diagnosis, or treatment. Do not use this information to make medical decisions.

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