Bicarbonate Deficit Calculator

About this calculator

The bicarbonate deficit is a bedside estimate used in metabolic acidosis, calculated as 0.4 × body weight (kg) × (24 − measured HCO₃⁻), where 0.4 approximates the bicarbonate space (roughly 40% of body weight) that the ion distributes into, and 24 mEq/L is the typical normal serum bicarbonate target. The result is the estimated total mEq of bicarbonate needed to close the gap between the patient's current HCO₃⁻ and a normal value.

This calculation is used in emergency medicine and critical care when evaluating patients with severe metabolic acidosis — from diabetic ketoacidosis, renal tubular acidosis, severe diarrhea, or lactic acidosis — to estimate the scale of the bicarbonate gap before any correction is considered. Nephrologists and intensivists also use the same 0.4 × weight formula (sometimes 0.5 in more severe or chronic acidosis) when assessing chronic kidney disease patients with persistently low bicarbonate.

This calculator takes body weight and the patient's measured HCO₃⁻ and returns the estimated deficit in mEq, giving clinicians a starting reference figure for how large the underlying acid-base disturbance is.