Cortisol to ACTH Ratio Calculator

About this calculator

Cortisol and ACTH (adrenocorticotropic hormone) work as a feedback loop: the pituitary releases ACTH to stimulate the adrenal glands to produce cortisol, and rising cortisol normally suppresses further ACTH release. Looking at their ratio rather than either value alone helps distinguish between different causes of adrenal dysfunction — a low ratio can point toward primary adrenal insufficiency (Addison's disease, where ACTH is high but the adrenals can't respond), while patterns of both being low or both elevated suggest different pituitary or ectopic causes.

This calculator simply divides cortisol (μg/dL) by ACTH (pg/mL) to produce that ratio. It's meant as a quick reference for students and clinicians reviewing lab panels — the ratio's clinical interpretation depends on the full clinical picture and reference ranges from the testing lab, so this is for reference only and not medical advice.