Calculate the aldosterone-to-renin ratio (ARR) from aldosterone and plasma renin activity or direct renin, with unit conversion and optional lab cutoffs.

Use quantified lab values, not “less than” detection limits. PRA and direct renin use different units and cutoffs.

Lab thresholds and collection context
Optional; enter your lab’s assay-specific cutoff. No universal default.

Medical disclaimer: This calculator is for educational purposes only and is not medical advice or a diagnosis. ARR/RAR interpretation depends on the lab method/units and clinical context (including medications and sample collection conditions). Do not change medications or treatment based on this result—review results with a licensed clinician.

Clinical context (important)

  • ARR is commonly used as a screening metric for primary aldosteronism, but cutoffs vary by assay, units, and lab reporting. Further testing may be needed depending on the results and clinical context; interpretation belongs with a clinician.
  • Many factors can change renin/aldosterone results (for example: diuretics, ACE inhibitors/ARBs, beta blockers, mineralocorticoid receptor antagonists, posture/time of day, sodium intake, pregnancy, and kidney disease).
  • Plasma renin can be reported as PRA or direct renin concentration (DRC); they are not interchangeable without method-specific guidance. Check your lab report and discuss with your clinician (see the Endocrine Society guideline for primary aldosteronism screening/diagnosis).

Unit conversion notes

The pmol/L to ng/dL aldosterone conversion used here is based on aldosterone molecular weight (MW ≈ 360.44 g/mol): 1 pmol/L ≈ 0.0360444 ng/dL. If your lab uses different reporting conventions, always follow the lab’s documentation.

ARR and RAR Formula

The following example problems outline the steps and information needed to calculate the aldosterone-to-renin ratio (ARR) and its inverse, the renin-to-aldosterone ratio (RAR).

ARR = (A) / (R) \ RAR = (R) / (A) = (1) / (ARR)

Variables:

  • ARR is the aldosterone-to-renin ratio (A/R), commonly used for screening (units depend on reporting, e.g., (ng/dL)/(ng/(mL-h))).
  • RAR is the renin-to-aldosterone ratio (R/A), the inverse of ARR (RAR = 1/ARR; e.g., (ng/(mL-h))/(ng/dL)).
  • A is the mass concentration of aldosterone (e.g., ng/dL). 
  • R is plasma renin activity (e.g., ng/(mL-h)) or direct renin concentration (e.g., mIU/L), using the corresponding method-specific ARR units and cutoffs. 

ARR is calculated by dividing aldosterone by the selected renin measurement (ARR = A/R); PRA and DRC ratios have different units and interpretation. The Renin/Aldosterone ratio shown here (RAR) is the reciprocal (RAR = R/A = 1/ARR).

How to Calculate ARR (and RAR)?

The following steps outline how to calculate ARR and RAR.

  1. First, determine the mass concentration of aldosterone (A) from your lab report (e.g., ng/dL). 
  2. Next, identify whether your report gives plasma renin activity or direct renin concentration (R), and choose matching units. Do not substitute one method’s cutoff for the other. 
  3. Use the formulas: ARR = A/R and RAR = R/A (= 1/ARR).
  4. Finally, calculate the ratio(s) and compare with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

mass concentration of aldosterone (ng/dL) = 30

plasma renin activity (ng/(mL-h)) = 14

ARR = A/R = 30/14 ≈ 2.143
RAR = R/A = 14/30 ≈ 0.467