Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Anion gap
32.0
Delta gap
20.0
Delta ratio
1.43
Interpretation
Pure anion-gap metabolic acidosis
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How to use this
- 1Enter sodium (mEq/L).
- 2Enter chloride (mEq/L).
- 3Enter bicarbonate (hco3) (mEq/L).
- 4Enter assumed normal anion gap (mEq/L).
- 5Read your anion gap on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
The delta ratio compares the rise in anion gap to the fall in bicarbonate to reveal whether a mixed acid-base disorder is hiding alongside an obvious anion-gap metabolic acidosis. A ratio between roughly 1 and 2 suggests a pure anion-gap metabolic acidosis (the gap rose about as much as the bicarbonate fell, as expected from simple buffering). A ratio below 1 suggests a concurrent non-gap (hyperchloremic) metabolic acidosis — bicarbonate fell more than the gap rose, meaning something is consuming bicarbonate beyond what the elevated anion gap alone explains, common with concurrent diarrhea or renal tubular acidosis in a patient who also has ketoacidosis or lactic acidosis. A ratio above 2 suggests a concurrent metabolic alkalosis or a pre-existing elevated bicarbonate — the bicarbonate didn't fall as much as expected given the size of the gap, sometimes seen in vomiting-plus-ketoacidosis or chronic compensated respiratory acidosis. This is a pattern-recognition tool that requires a reliable baseline (usually assumed normal) HCO3 and anion gap. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.
Worked example
Using the values the calculator loads with:
Inputs
- Sodium: 138 mEq/L
- Chloride: 96 mEq/L
- Bicarbonate (HCO3): 10 mEq/L
- Assumed normal anion gap: 12 mEq/L
Results
- Anion gap: 32
- Delta gap: 20
- Delta ratio: 1.43
- Interpretation: Pure anion-gap metabolic acidosis
What each field means
Inputs
- Sodium (mEq/L)
- The sodium used in the calculation, measured in mEq/L. Starts at 138 mEq/L so you have a working example on load. Accepted range: 100–170 mEq/L.
- Chloride (mEq/L)
- The chloride used in the calculation, measured in mEq/L. Starts at 96 mEq/L so you have a working example on load. Accepted range: 70–130 mEq/L.
- Bicarbonate (HCO3) (mEq/L)
- The bicarbonate (hco3) used in the calculation, measured in mEq/L. Starts at 10 mEq/L so you have a working example on load. Accepted range: 2–40 mEq/L.
- Assumed normal anion gap (mEq/L)
- The assumed normal anion gap used in the calculation, measured in mEq/L. Starts at 12 mEq/L so you have a working example on load. Accepted range: 4–16 mEq/L.
Results
- Anion gap
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Delta gap
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Delta ratio
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Interpretation
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
What does a delta ratio below 1 tell me?
It tells you bicarbonate has fallen more than the anion gap rise alone can explain, pointing to an additional non-gap (hyperchloremic) metabolic acidosis on top of the gap acidosis — for example, a patient in diabetic ketoacidosis who has also had significant diarrhea or large-volume saline resuscitation.
What does a delta ratio above 2 mean?
It suggests bicarbonate is higher than expected given the size of the anion gap, pointing to a concurrent metabolic alkalosis or a chronically elevated baseline bicarbonate (as in chronic respiratory acidosis with renal compensation), partially masking the expected bicarbonate drop from the gap acidosis.
Why assume a normal anion gap of 12?
12 mEq/L is a commonly used average baseline for a 'normal' unmeasured anion gap, though normal ranges vary by lab and by whether potassium is included in the calculation (roughly 8-12 without potassium, 10-16 with it). Using your lab's actual reference range as the 'normal' input improves accuracy over assuming a fixed value.
Is the delta ratio reliable in every patient?
It's a useful pattern-recognition tool but has real limitations — it assumes a fairly stable relationship between gap rise and bicarbonate fall that doesn't always hold, particularly with severe acidosis, renal failure, or multiple simultaneous processes. Use it to raise suspicion for a mixed disorder, then confirm with full clinical correlation, not as a standalone diagnosis.
Accuracy and limitations
- Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
- Results do not account for medical conditions, medication, or pregnancy.
- Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Delta Gap / Delta Ratio Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/delta-gap-ratio
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/delta-gap-ratio" target="_blank" rel="noopener">Delta Gap / Delta Ratio Calculator — RevenueLab</a> (2026).</p>
Source: [Delta Gap / Delta Ratio Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/delta-gap-ratio) (2026).