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Delta Gap & Delta-Delta Ratio Calculator
The delta gap and delta-delta ratio are the reasoning steps that turn a single anion gap into a picture of concurrent acid-base disorders, and this calculator surfaces them alongside the gap itself. The delta gap is how far the anion gap has risen above normal (measured AG − 12), and the delta-delta ratio compares that rise to the fall in bicarbonate: Δ/Δ = (AG − 12) ÷ (24 − HCO₃). A ratio below 1 suggests a coexisting normal-anion-gap (hyperchloremic) acidosis, while a ratio above 2 suggests a coexisting metabolic alkalosis or a pre-existing high bicarbonate — mixed disorders a bare subtraction never reveals. Start from the anion gap of Na − (Cl + HCO₃), optionally add potassium or correct for albumin, and read the delta gap and its interpretation. Because the normal gap is lab-dependent (classically 8–12, ~3–11 on modern analyzers), the reference used here is 12; adjust your interpretation to your own lab. This is an interpretation aid, not a diagnosis — verify clinically. Free, private, browser-only.
delta gap = measured AG − 12 (the rise above normal)
- Δ/Δ = (AG − 12) ÷ (24 − HCO₃) — mixed-disorder ratio
- Δ/Δ < 1 → coexisting NAGMA; > 2 → coexisting metabolic alkalosis
Frequently asked questions
What is the delta-delta ratio?
The delta-delta ratio compares the rise in the anion gap to the fall in bicarbonate: Δ/Δ = (measured AG − 12) ÷ (24 − HCO₃). It detects mixed acid-base disorders — a ratio below 1 suggests a coexisting normal-anion-gap (hyperchloremic) acidosis, and a ratio above 2 suggests a coexisting metabolic alkalosis or a pre-existing high bicarbonate. It is an interpretation aid, not a diagnosis.
What does a delta gap tell you?
The delta gap (measured anion gap − 12) is the amount the gap has risen above normal. Compared with the fall in bicarbonate, it shows whether the whole change in bicarbonate is explained by the high-anion-gap acidosis or whether a second disorder is also present. It is the step that turns one number into a picture of concurrent disorders.