Winters' formula calculator

Winters' Formula

Winters' Formula — Expected pCO₂

Input	Value
Serum Bicarbonate (HCO₃⁻) mEq/L
Results
Expected pCO₂ (low end)	mmHg
Expected pCO₂ (high end)	mmHg

Interpretation
pCO₂ in expected range	Appropriate respiratory compensation — Pure metabolic acidosis with adequate compensation.
pCO₂ > expected	Concurrent respiratory acidosis — Inadequate compensation; concurrent respiratory acidosis present.
pCO₂ < expected	Concurrent respiratory alkalosis — Overcompensation; concurrent respiratory alkalosis present.

References
Winters RW, et al. Studies of Acid Base Disturbances. J Clin Invest. 1956;35:311-318. Formula: Expected pCO₂ = 1.5 × [HCO₃⁻] + 8 (± 2) Albert MS, Dell RB, Winters RW. Quantitative displacement of acid-base equilibrium in metabolic acidosis. Ann Intern Med. 1967;66(2):312-322.