Albumin/Globulin (A/G) Ratio Calculator
Calculate A/G ratio from albumin with reported globulin or same-panel total protein; total-protein mode also shows calculated globulin with laboratory-specific interpretation limits.
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About
This calculator compares serum albumin with a reported globulin value or with globulin calculated as total protein minus albumin. The ratio is unitless, while globulin represents a broad non-albumin protein fraction rather than one protein. [1, 2]
Interpretation requires the absolute protein values, the reporting laboratory’s methods and reference intervals, specimen context, and other evidence.
Formula
Interpretation
What does a low or high A/G ratio mean?
A lower A/G ratio means albumin is lower relative to globulin; that arithmetic can result from lower albumin, higher globulin, or both. A higher A/G ratio means albumin is higher relative to globulin and can result from higher albumin, lower globulin, or both. Review the absolute albumin, globulin, and total-protein values and use the reporting laboratory's own reference interval. MedlinePlus lists several possible clinical contexts for abnormal results, but the ratio alone does not establish a cause or diagnosis. [1, 5, 6]
What calculated globulin does—and does not—represent
Routine chemistry calculated globulin is total protein minus albumin. It includes proteins across alpha, beta, and gamma regions; it is not gamma globulin alone, an IgG/IgA/IgM concentration, or a test that can display a monoclonal peak. Serum protein electrophoresis separates protein fractions, immunofixation characterizes certain proteins, and quantitative immunoglobulin tests measure different analytes. [2, 3, 7]
Reported versus calculated globulin
| Input mode | Values used | Calculator arithmetic | Key limitation |
|---|---|---|---|
| Reported globulin | Albumin and a report’s globulin value | Albumin ÷ globulin | This page cannot determine how the report produced globulin |
| Total protein | Albumin and total protein | Subtract albumin, then divide | Sensitive to method and same-panel consistency |
Reported globulin
- Values used
- Albumin and a report’s globulin value
- Calculator arithmetic
- Albumin ÷ globulin
- Key limitation
- This page cannot determine how the report produced globulin
Total protein
- Values used
- Albumin and total protein
- Calculator arithmetic
- Subtract albumin, then divide
- Key limitation
- Sensitive to method and same-panel consistency
Why laboratory method matters
Total protein commonly uses the biuret reaction, while albumin is often measured with dye-binding methods. Albumin methods can differ systematically; because albumin is both subtracted to obtain calculated globulin and used in the ratio numerator, that difference can change calculated globulin and A/G ratio together. Method-specific calculated-globulin cutoffs in the Jolles study differed between bromocresol green and bromocresol purple, and a 2026 calculated-globulin reference interval was explicitly specific to Roche biuret total protein plus bromocresol-green albumin methods. Reference intervals from different laboratories, methods, and populations are therefore not mechanically interchangeable. This page assigns no universal normal, low, or high category. [2, 3, 4, 5]
The ratio cannot replace the absolute concentrations
Albumin 4.0 g/dL divided by globulin 2.0 g/dL and albumin 2.0 g/dL divided by globulin 1.0 g/dL both equal 2.00. The identical ratio does not make the absolute protein concentrations or their context identical. Looking only at the ratio can conceal simultaneous decreases or increases, so retain albumin, globulin, and total protein values.
A/G ratio compared with other protein tests
| Test or calculation | Output | Why it is not interchangeable with A/G ratio |
|---|---|---|
| Albumin | One concentration | Does not describe other proteins |
| Total protein | Combined major serum proteins | Does not separate albumin from globulin |
| Calculated globulin | Total protein − albumin | Total non-albumin fraction, not one immunoglobulin |
| A/G ratio | Relative albumin/globulin value | Can hide different absolute concentrations |
| Protein or “gamma” gap | Total protein − albumin | A concentration difference, not a ratio; the nickname does not make it gamma-only |
| Serum protein electrophoresis | Protein-fraction pattern | Separates migration regions and may show a discrete peak |
| Immunofixation | Protein characterization | Not a simple chemistry ratio |
| Quantitative immunoglobulins | IgG, IgA, and IgM concentrations | Do not equal total globulin |
Albumin
- Output
- One concentration
- Why it is not interchangeable with A/G ratio
- Does not describe other proteins
Total protein
- Output
- Combined major serum proteins
- Why it is not interchangeable with A/G ratio
- Does not separate albumin from globulin
Calculated globulin
- Output
- Total protein − albumin
- Why it is not interchangeable with A/G ratio
- Total non-albumin fraction, not one immunoglobulin
A/G ratio
- Output
- Relative albumin/globulin value
- Why it is not interchangeable with A/G ratio
- Can hide different absolute concentrations
Protein or “gamma” gap
- Output
- Total protein − albumin
- Why it is not interchangeable with A/G ratio
- A concentration difference, not a ratio; the nickname does not make it gamma-only
Serum protein electrophoresis
- Output
- Protein-fraction pattern
- Why it is not interchangeable with A/G ratio
- Separates migration regions and may show a discrete peak
Immunofixation
- Output
- Protein characterization
- Why it is not interchangeable with A/G ratio
- Not a simple chemistry ratio
Quantitative immunoglobulins
- Output
- IgG, IgA, and IgM concentrations
- Why it is not interchangeable with A/G ratio
- Do not equal total globulin
These tests answer different questions; this calculator does not choose which test should be performed. [7]
Specimen and comparability limits
Use values from a compatible same specimen or laboratory panel. Do not mix serum and plasma without laboratory confirmation: a 2024 study found meaningful specimen-matrix effects on reference intervals for total protein, albumin, and globulin. Hydration or volume status, intravenous fluid, specimen handling, different laboratories, different methods, or different collection times can reduce comparability. Pediatric, pregnancy, and special-disease contexts require the applicable laboratory information. This page cannot determine a cause or select SPEP, immunofixation, liver or kidney testing, nutrition intervention, referral, medication, or treatment. [1, 3, 6]
Worked arithmetic examples
Reported globulin: albumin 4.0 g/dL and reported globulin 2.5 g/dL give total-protein arithmetic 6.5 g/dL and raw ratio 1.6, displayed 1.60.
Total protein: albumin 4.0 g/dL and total protein 6.5 g/dL give calculated globulin 2.5 g/dL and ratio 1.60.
SI and mixed units: 40 g/L albumin with 65 g/L total protein—or 4.0 g/dL albumin with 65 g/L total protein—normalizes to the same values and gives ratio 1.60. [8]
Invalid subtraction: total protein equal to or below albumin produces no ratio and is not clamped into zero or a negative globulin. Check the units, specimen, report, and entries.
References
- MedlinePlus. Total Protein and Albumin/Globulin (A/G) Ratio. U.S. National Library of Medicine.
- Busher JT. Serum Albumin and Globulin. In: Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. 1990. Chapter 101.
- Jolles S, Borrell R, Zouwail S, et al. Calculated globulin (CG) as a screening test for antibody deficiency. Clin Exp Immunol. 2014;177(3):671–678. PMID 24784320. PMCID PMC4137851. doi:10.1111/cei.12369.
- McGinlay JM, Payne RB. Serum albumin by dye-binding: bromocresol green or bromocresol purple? The case for conservatism. Ann Clin Biochem. 1988;25(Pt 4):417–421. PMID 3214125. doi:10.1177/000456328802500417.
- Flannery C, Griffin A, Quinn J, Loughrey C, Srinivasan S. Establishment of a reference interval for calculated globulin on the Roche platform. Ann Clin Biochem. 2026;63(2):105–113. Epub 2025 Jul 29. PMID 40728856. doi:10.1177/00045632251367264.
- Militello L, El-Khoury JM, Durant TJS. Accounting for differences between serum and plasma: An indirect approach to derive reference intervals for total protein, albumin, and globulin. Clin Chim Acta. 2024;562:119851. PMID 38977172. doi:10.1016/j.cca.2024.119851.
- MedlinePlus. Protein Electrophoresis by Immunofixation Blood Test. U.S. National Library of Medicine.
- National Institute of Standards and Technology. NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically.
FAQ
The A/G ratio divides albumin by globulin and is unitless. The protein or gamma gap subtracts albumin from total protein and remains a concentration. Neither calculation isolates gamma globulin.
Sources: [2]
Yes, if each unit is selected correctly. The calculator normalizes each value independently using 1 g/dL = 10 g/L before subtraction or division, without intermediate rounding.
Sources: [8]
Albumin is subtracted from total protein to calculate the denominator. Equality would give a zero denominator, while a lower total protein would give a negative globulin. Neither produces a reportable ratio here.
Sources: [2]
A ratio records a relative relationship. Albumin 4.0 divided by globulin 2.0 and albumin 2.0 divided by globulin 1.0 both equal 2.00, even though all absolute concentrations differ.
Sources: [1]
No. A lower ratio means albumin is lower relative to globulin and can reflect lower albumin, higher globulin, or both; a higher ratio means albumin is higher relative to globulin and can reflect higher albumin, lower globulin, or both. Use the reporting laboratory's interval and review the absolute albumin, globulin, and total-protein values. A ratio alone cannot diagnose liver or kidney disease, malnutrition, infection, inflammation, an immune disorder, or a monoclonal protein.
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Disclaimer
Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.