What is the Anion Gap Calculator?
Calculate an unmeasured-ion gap from sodium, chloride, bicarbonate, and albumin reported from the same laboratory sample. The primary result uses the potassium-free anion-gap equation. A separate albumin adjustment is displayed for educational comparison because albumin contributes to the unmeasured anion pool.
When the same clinical record includes the required inputs, the Serum Osmolality Calculator can calculate estimated serum osmolality from sodium, glucose, and blood urea nitrogen.
This page is designed for transparent arithmetic, not automated medical judgment. Use values from the same encounter and measurement period, preserve the stated units, and record which equation version was used. A correct calculation can still be clinically inappropriate when the population, timing, laboratory method, or required protocol does not match the equation.
How to use the Anion Gap Calculator
Collect Serum sodium, Serum chloride, Serum bicarbonate, Serum albumin from a reliable source. Check identifiers and timestamps outside this page, confirm that the values belong together, and never estimate a clinical finding merely to complete a form.
- Confirm the calculator, equation version, intended population, units, and applicable institutional protocol.
- Enter every requested value or selection exactly as documented. The calculator rejects blank and unsupported entries.
- Select Calculate Anion Gap, then review the primary result, status badge, scale, four supporting values, safety note, and calculation steps.
Independently verify any result that could influence care. Recheck decimal placement, unit conversion, age or sex convention, component definitions, laboratory bounds, and whether a value was measured before or after an intervention.
Formula and calculation method
The primary result uses the potassium-free anion-gap equation. A separate albumin adjustment is displayed for educational comparison because albumin contributes to the unmeasured anion pool. Intermediate arithmetic retains extra precision and the displayed result is rounded for readability. The calculation runs locally in the browser.
Clinical equations are compact models of selected information. They do not include every symptom, examination finding, comorbidity, medication, measurement limitation, or change over time. Where the source method applies bounds, weights, or categories, those rules are stated on this page and reflected in the steps.
How to understand the result
The large gradient figure is the primary calculated value or score. The colored cards show inputs, intermediate values, component totals, or an alternative representation. The visual scale is an orientation aid only; it is not a diagnosis, alarm threshold, treatment order, or substitute for a validated clinical pathway.
For a separate but related calculation, use the Corrected Sodium Calculator to estimate a glucose-adjusted serum sodium value during hyperglycemia.
Interpretation must consider why the calculation was ordered, who the equation was validated for, whether the patient is stable, and whether repeat or direct measurement is available. Clinical scores that include judgment-based findings should be completed only by someone trained to assess those findings.
When results appear inconsistent with the clinical picture, stop and verify the original data rather than forcing the value into an expected category. Trends may be more informative than one isolated result, but only when the method and units remain comparable.
Worked example and practical interpretation
Sodium 140, chloride 104, and bicarbonate 24 produce an unadjusted anion gap of 12 mEq/L before any albumin adjustment.
If that question is relevant to the same review, the eGFR Calculator provides a distinct method to estimate adult kidney filtration with the race-free 2021 CKD-EPI creatinine equation.
The example demonstrates the displayed equation rather than a recommendation for a real patient. Replace every example value with verified information, then compare the result with the source document, applicable guideline, and local workflow. Do not copy an example result into a medical record.
Accuracy, safety, and limitations
Reference intervals vary by laboratory and analyzer. The albumin adjustment is an approximation and the result cannot identify a cause of acid-base disturbance by itself.
Anion Gap Calculator FAQs
Sources and methodology
Authoritative and primary sources support the equation, component definitions, and limitations. They do not endorse this website or any result entered here. Check publication updates and the protocol that applies in the clinical setting.