Winters Formula Calculator
Assess respiratory compensation in metabolic acidosis using Winters' equation
Calculate Expected pCO₂ Compensation
Normal range: 23-30 mmol/L. Enter low value for metabolic acidosis assessment.
Enter to assess adequacy of respiratory compensation
Example Calculations
Appropriate Compensation
Patient: HCO₃⁻ = 15 mmol/L (metabolic acidosis)
Winters Formula: pCO₂ = (1.5 × 15) + 8 = 30.5 ± 2 mmHg
Expected Range: 28.5 - 32.5 mmHg
Actual pCO₂: 30 mmHg → Appropriate compensation
Under-compensation
Patient: HCO₃⁻ = 12 mmol/L (severe metabolic acidosis)
Winters Formula: pCO₂ = (1.5 × 12) + 8 = 26 ± 2 mmHg
Expected Range: 24 - 28 mmHg
Actual pCO₂: 35 mmHg → Under-compensation (possible mixed disorder)
Winters Formula
Formula
Purpose
Predict expected respiratory compensation in metabolic acidosis
Units
HCO₃⁻ in mmol/L, pCO₂ in mmHg
Range
±2 mmHg accounts for physiological variation
Normal Values
Bicarbonate (HCO₃⁻)
23 - 30 mmol/L
Normal range
Arterial pCO₂
35 - 45 mmHg
4.7 - 6.0 kPa
Metabolic Acidosis
HCO₃⁻ < 23 mmol/L
Triggers respiratory compensation
pH Range
7.35 - 7.45
Normal arterial pH
Clinical Applications
Metabolic Acidosis
Assess respiratory compensation adequacy
Mixed Disorders
Identify coexisting respiratory disorders
ICU Monitoring
Track acid-base status in critical patients
Emergency Medicine
Rapid assessment of compensation
Metabolic Acidosis Causes
High Anion Gap
- • Diabetic ketoacidosis
- • Lactic acidosis
- • Renal failure
- • Toxin ingestion
Normal Anion Gap
- • Diarrhea
- • Renal tubular acidosis
- • Carbonic anhydrase inhibitors
- • Ureterosigmoidostomy
Understanding Winters Formula
What is Winters Formula?
Winters formula predicts the expected respiratory compensation (pCO₂) in patients with metabolic acidosis. It helps clinicians assess whether the respiratory system is appropriately compensating for the metabolic disorder.
Clinical Significance
- •Evaluates adequacy of respiratory compensation
- •Identifies mixed acid-base disorders
- •Guides clinical assessment and treatment
- •Monitors patient's overall physiologic response
Formula Components
pCO₂ = (1.5 × HCO₃⁻) + 8 ± 2