The acid base and anion gap calculators sit on the same electrolyte arithmetic but answer different questions. Both compute the anion gap as sodium minus the sum of chloride and bicarbonate. The acid base calculator wraps that calculation in pH and PCO2 pattern language — acidemia, alkalemia, or normal pH — and adds an albumin-corrected gap. The anion gap calculator stays focused on the gap itself, adding an optional potassium term and its own albumin correction. The pages cross-reference each other: the anion gap page recommends pairing its result with pH and PaCO2 from the acid base calculator, and the acid base page notes it overlaps with the anion gap calculator while adding pH and PCO2 language.
What each calculator does
The acid base calculator reads six values: pH, PCO2, bicarbonate, chloride, sodium, and albumin. It classifies pH below 7.35 as acidemia, above 7.45 as alkalemia, and 7.35 through 7.45 as normal pH, while displaying PCO2 and bicarbonate without classifying compensation or mixed disorders. The anion gap is sodium − (chloride + bicarbonate), and the albumin-corrected gap is the gap plus 2.5 × (4.4 − albumin). Gap values display with one decimal, the gap item is flagged when it is above 16 or below 8, and the primary interpretation is flagged when pH falls outside 7.35–7.45. The page explicitly does not apply Winter’s formula, expected PCO2, expected bicarbonate, delta gap, or chronic-versus-acute compensation rules. In the worked example — pH 7.30, PCO2 40, bicarbonate 18, chloride 100, sodium 140, albumin 4.0 — the result is Acidemia with a gap of 22.0 mEq/L flagged Elevated and a corrected gap of 23.0 mEq/L.
The anion gap calculator takes sodium, chloride, and bicarbonate in mEq/L, with two switches. By default the gap is sodium − (chloride + bicarbonate) compared with a 3 to 11 mEq/L reference range; with potassium switched on the formula becomes sodium + potassium − (chloride + bicarbonate) and the reference range changes to 5 to 16 mEq/L. When albumin correction is selected, the calculator adds 2.5 × (4.0 − albumin) to the gap — but the interpretation text still follows the uncorrected gap. The result displays to one decimal place. In the worked example, sodium 140, chloride 102, and bicarbonate 24 give 14.0 mEq/L, flagged high against the default 11 mEq/L upper limit; with albumin 3.0 the corrected gap is 16.5 mEq/L; with potassium on, the same electrolytes give 18.0 mEq/L against the 5–16 range.
Side-by-side
| Acid base calculator | Anion gap calculator | |
|---|---|---|
| Inputs | pH, PCO2, bicarbonate, chloride, sodium, albumin | Sodium, chloride, bicarbonate; optional potassium and albumin |
| Core gap formula | Sodium − (chloride + bicarbonate) | Sodium − (chloride + bicarbonate); with potassium on, sodium + potassium − (chloride + bicarbonate) |
| Albumin correction | Gap + 2.5 × (4.4 − albumin) | Gap + 2.5 × (4.0 − albumin) |
| Flag thresholds | Gap above 16 or below 8; pH outside 7.35–7.45 | Above 11 or below 3; with potassium, above 16 or below 5 |
| Pattern language | Acidemia / alkalemia / normal pH; no compensation classification | None — no pH input |
| Display | One decimal for gap values | One decimal |
When to use which
Use the acid base calculator when your question includes pH and ventilation: you have blood gas values and want the pH classified, the anion gap computed, and the albumin-corrected gap shown, with PCO2 and bicarbonate laid out for clinical reading. It deliberately stops short of compensation analysis, so treat its labels as pattern language, not a complete interpretation.
Use the anion gap calculator when your question is specifically the electrolyte gap: you want the sodium-minus-chloride-plus-bicarbonate number, an optional potassium-included variant with its own reference range, and an optional albumin correction. Because its interpretation follows the uncorrected gap, check the corrected value yourself when albumin is low. For the full picture, follow the anion gap page’s own advice and pair the result with pH and PaCO2 from the acid base calculator.
Limits and disclaimer
Both pages are educational only and are not medical advice, diagnosis, triage, or treatment guidance. Neither diagnoses diabetic ketoacidosis, lactic acidosis, poisoning, kidney failure, or any other condition. Real acid-base interpretation depends on symptoms, oxygenation, sampling type, timing, medications, renal function, lactate, ketones, and the full clinical context — and a normal pH does not rule out a mixed disorder, because opposing respiratory and metabolic processes can partially offset each other. Reference ranges also differ by analyzer and laboratory method, so use the range printed by the laboratory whenever it differs from a calculator’s embedded thresholds.