This version was machine-translated from German and has not been medically reviewed. The authoritative version is the German version.

Winter's formula

Expected pCO₂ in metabolic acidosis: 1.5 × HCO₃ + 8 ± 2

Scientific basis

Reference range of your own laboratory

Anion gap and delta ratio depend on the measurement method for sodium and chloride. The reference values used here (AG 12, HCO₃⁻ 24) are conventions of the cited papers; your own laboratory's reference range takes precedence.

Calculation aid for healthcare professionals: the calculator reproduces what the sources cited assign to the inputs. Clinical assessment and every treatment decision remain with the treating physician. Inputs and results are not stored.

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Sources

Serum anion gap: its uses and limitations in clinical medicine (Clin J Am Soc Nephrol 2:162–174) Kraut JA, Madias NE, 2007. Review article (freely accessible)
Anion gap and hypoalbuminemia (Crit Care Med 26:1807–1810) Figge J, Jabor A, Kazda A, Fencl V, 1998. Original paper (albumin correction 2.5 mEq/l per g/dl)
The delta (Δ) gap: an approach to mixed acid-base disorders (Ann Emerg Med 19:1310–1313) Wrenn K, 1990. Original paper
Quantitative displacement of acid-base equilibrium in metabolic acidosis (Ann Intern Med 66:312–322) – “Winter formula” Albert MS, Dell RB, Winters RW, 1967. Original paper
Physiological approach to assessment of acid-base disturbances (N Engl J Med 371:1434–1445) – Table 2: Expected compensatory responses Berend K, de Vries AP, Gans RO, 2014. Review article
Metabolic acidosis: pathophysiology, diagnosis and management (Nat Rev Nephrol 6:274–285) Kraut JA, Madias NE, 2010. Review article (bicarbonate deficit, volume of distribution)

Scientific basis last reviewed: September 2026.

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Note

Calculation aid for healthcare professionals. Percentiles and z-scores describe the position of a measured value in the reference population; clinical assessment remains with the treating physician.