HOMA-IR Calculator

Fasting glucose times fasting insulin, divided by 405 when glucose is in mg/dL and by 22.5 when it is in mmol/L. The two divisors differ by the factor 18 that separates the units, so picking the wrong one is an eighteen-fold error. The index estimates insulin resistance; it does not diagnose anything.

HOMA-IR condenses two values from one fasting blood draw — glucose and insulin — into a single figure that estimates how strongly the body resists insulin. Higher values point toward more resistance, lower ones toward cells that respond well. The arithmetic is one multiplication and one division, and the whole risk sits in the divisor, because it belongs to the glucose unit: 405 when glucose is reported in mg/dL, 22.5 when it is reported in mmol/L, with insulin in µU/mL either way. The preset values, 100 mg/dL and 10 µU/mL, give 100 × 10 ÷ 405 = 2.47. A molar report of 5.5 mmol/L with 8 µU/mL gives 5.5 × 8 ÷ 22.5 = 1.96. The two divisors stand in a ratio of 18, exactly the factor between the glucose units, so both routes describe the same blood. Read the figure against your own laboratory's reference range rather than a fixed line. The orientation bands on this page sort results in a common way, but there is no universal cut-off: the thresholds move with laboratory, assay and population. Both values also have to come from the same fasting sample, since food raises glucose and insulin together and would inflate the index. HOMA-IR is a screening and research index. It replaces neither a laboratory measurement nor a diagnosis, which rests on defined criteria such as fasting glucose, HbA1c or an oral glucose tolerance test.