HOMA-IR Calculator

Background.

Ask whether a HOMA-IR of 2.8 is normal and you run into a refusal from the people best placed to answer. The Diabetes Trials Unit at the University of Oxford, which looks after the homeostasis model, says there is no universal normal value for HOMA indices: results depend on the particular glucose and insulin assays a laboratory uses, and for that reason no thresholds for normal and abnormal have been defined. Every "normal range" quoted online belongs to somebody's study population, measured on somebody's insulin assay, under somebody's definition of metabolic syndrome.

What the index does capture is a real physiological pattern. When muscle, liver and fat respond less readily to insulin, the pancreas compensates by releasing more of it, and for a long time fasting glucose can stay where it was. A glucose result on its own misses that phase entirely. Put the fasting insulin beside it and the compensation becomes visible: the same glucose held in place by twice the insulin describes a body working twice as hard to keep it there.

David Matthews and colleagues at Oxford turned that idea into arithmetic in 1985. Their linear approximation, now called HOMA1, multiplies fasting insulin in µU/mL by fasting glucose in mmol/L and divides by 22.5, a constant chosen so that their reference adult scores exactly 1. Against the glucose clamp, the laborious reference method for measuring insulin sensitivity, the estimate correlated at Rs = 0.88 — yet the same paper warned that a coefficient of variation of 31% limits what it can say about one person.

Those two facts shape the calculator. It reports HOMA1-IR and its reciprocal, HOMA1-%S. It compares your result with a cut-off you choose, pre-filled with 2.05, one Spanish population study's value for non-diabetic men rather than any standard. It converts mg/dL using the exact molar mass of glucose. And it diagnoses nothing: HOMA-IR is a research measure that can prompt a conversation with a clinician and can follow change over time in one laboratory, supporting clinical judgement rather than replacing it.

What is homa-ir calculator?

HOMA-IR, the homeostasis model assessment of insulin resistance, is a single number built from a fasting glucose and a fasting insulin taken from the same blood draw. The model treats the pair as the resting balance point of a feedback loop — glucose prompting the pancreas to secrete insulin, insulin restraining the liver's release of glucose — and reads the position of that balance point as a measure of how resistant the body is to insulin's action. HOMA1-IR is the 1985 linear shortcut to the model; HOMA2, a computer model the same Oxford group released in 1998, solves the physiology numerically and gives different values. The companion HOMA1-%S expresses the same information as sensitivity, a percentage of the model's normal reference population, and equals 100 divided by HOMA1-IR. Neither is a diagnostic criterion for any condition.

How to use this calculator.

1. 01Use glucose and insulin from the same fasting sample, drawn after at least eight hours without food or caloric drinks. A glucose from one visit paired with an insulin from another does not describe a single balance point.
2. 02Enter the glucose and pick its unit. Switching the unit converts whatever is already in the box — 90 mg/dL becomes 4.9957 mmol/L — so if you typed the number first and then realised the unit was wrong, re-enter the figure from your report.
3. 03Enter fasting insulin in µU/mL; a report that says mIU/L means the same number. If yours gives pmol/L, ask the laboratory for the µU/mL value or for its own conversion factor rather than using one found online.
4. 04Replace the 2.05 cut-off with the threshold your laboratory, clinician or study protocol uses. If you have none, keep the default but give the comparison little weight.
5. 05Read HOMA1-IR first, then the margin to your cut-off. A margin smaller than about 31% of the result sits inside the scatter the model's authors reported for a single measurement.
6. 06Take the index, both raw results and the laboratory's reference ranges to your clinician. One HOMA-IR is a reason to talk and perhaps repeat the test, not a diagnosis.

The formula.

HOMA1-IR = (I₀ × G₀) ÷ 22.5, where I₀ is fasting insulin in µU/mL and G₀ is fasting glucose in mmol/L. Oxford's HOMA FAQ gives the equation in exactly this form, and the EPIRCE investigators state the same expression, with the same units, independently. The divisor is the product of a reference fasting insulin of 5 µU/mL and a reference fasting glucose of 4.5 mmol/L, so a person at that reference point scores 1.0 and any result reads as a multiple of the reference.

Because the two measurements multiply, they trade off proportionally: a 20% rise in insulin moves the index exactly as far as a 20% rise in glucose. In practice fasting insulin varies far more from person to person than fasting glucose does, so the insulin result is usually what separates a high HOMA-IR from a low one.

Glucose entered in mg/dL is first divided by 18.0156, the number of mg/dL in one mmol/L of glucose. That factor follows from the molar mass of glucose, 180.156 g/mol, calculated from IUPAC's 2023 standard atomic weights for carbon, hydrogen and oxygen. Many sources give a mg/dL shortcut instead, insulin × glucose ÷ 405; since 405 is 22.5 × 18, the shortcut rounds the conversion factor to 18. At 90 mg/dL and 8 µU/mL the exact route gives 1.7762 and the shortcut 1.7778, a gap of under a tenth of a percent that explains small disagreements between tools and never changes an interpretation.

HOMA1-%S = 100 ÷ HOMA1-IR. The reciprocal is steep at the low end and flat at the high end: moving from 1 to 2 halves sensitivity from 100% to 50%, while moving from 4 to 5 takes it only from 25% to 20%. The margin is HOMA1-IR minus your cut-off, and the position line says "at or above" whenever the index equals or exceeds that cut-off. Glucose above 40 mmol/L (about 720 mg/dL) or insulin above 1,000 µU/mL is refused: such values lie far outside the fasting state the model describes, and an insulin that high usually means a pmol/L figure typed into the µU/mL field.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Matthews DR, Hosker JP, Rudenski AS, Naylor BA, Treacher DF, Turner RC. "Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma glucose and insulin concentrations in man." Diabetologia. 1985;28(7):412-419. doi:10.1007/BF00280883. Original model. Source of the feedback-loop premise, the clamp correlation Rs = 0.88, and the authors' own precision caveat (coefficients of variation 31% for insulin resistance and 32% for beta-cell deficit). Abstract open on PubMed (PMID 3899825); full text paywalled. Retrieved 29 July 2026.
2. [2]University of Oxford, Radcliffe Department of Medicine, Diabetes Trials Unit. "HOMA — Frequently Asked Questions." The custodians of HOMA. Source of the equation 'HOMA1_IR = (FPI x FPG)/22.5', of the statement that HOMA1 formulae provide 'only linear approximations of HOMA_%B and HOMA_IR, the inverse of HOMA_%S', and of the key scope limit: 'There is no absolute value for HOMA indices. These will depend on the specific assays used for glucose, insulin and C-peptide. Because of this, there are no defined thresholds for normal vs. abnormal values.' Retrieved 29 July 2026.
3. [3]University of Oxford, Radcliffe Department of Medicine, Diabetes Trials Unit. "HOMA Calculator" overview page: "The Homeostasis Model Assessment (HOMA) estimates steady state beta cell function (%B) and insulin sensitivity (%S), as percentages of a normal reference population." Source of the definition of %S as a percentage of a normal reference population. Retrieved 29 July 2026.
4. [4]Gayoso-Diz P, Otero-González A, Rodriguez-Alvarez MX, Gude F, García F, De Francisco A, Quintela AG. "Insulin resistance (HOMA-IR) cut-off values and the metabolic syndrome in a general adult population: effect of gender and age: EPIRCE cross-sectional study." BMC Endocrine Disorders. 2013;13:47. doi:10.1186/1472-6823-13-47. Independent statement of the equation and units ('fasting serum insulin (μU/ml) × fasting plasma glucose (mmol l⁻¹)/22.5'); source of the population cut-offs quoted on this page (men 1.85 ATPIII / 2.05 IDF; women 2.31 at 30, 2.07 at 50, 2.47 at 70; 3.46 at the 90th percentile) from 2,459 Spanish adults, and of the statement that cut-offs 'are different according to ethnicity, clinical methods of estimation, and metabolic conditions'. Open access; retrieved 29 July 2026.
5. [5]Wallace TM, Levy JC, Matthews DR. "Use and abuse of HOMA modeling." Diabetes Care. 2004;27(6):1487-1495. doi:10.2337/diacare.27.6.1487. The standard review of appropriate and inappropriate uses of HOMA, and of the relationship between the 1985 approximation formulae and the later computer model. Publisher full text paywalled; open bibliographic record with abstract at Oxford University Research Archive, retrieved 29 July 2026. Cited for the HOMA1/HOMA2 distinction only.
6. [6]International Union of Pure and Applied Chemistry, Commission on Isotopic Abundances and Atomic Weights. Standard atomic weights, 2023 abridged table: C = 12.011, H = 1.0080, O = 15.999. Used to derive the glucose molar mass 180.156 g/mol and hence the exact mg/dL-to-mmol/L factor of 18.0156 that this calculator uses in place of the rounded 18 embedded in the conventional 405 divisor. Retrieved 29 July 2026.