Enter the mass concentration of aldosterone (ng/dL) and the plasma renin activity (ng/(mL-h)) into the calculator to compute the aldosterone-to-renin ratio (ARR = A/R) and the inverse renin-to-aldosterone ratio (RAR = R/A). 

Aldosterone-to-Renin Ratio (ARR) Calculator

Quick Screen
Units and Assumptions
What It Means
Renin Method
Plasma Renin Activity (PRA)
Direct Renin (DRC)
Use the same assay style your lab report uses. PRA and direct renin use different screening cutoffs.
ARR cutoff
You can change this to match a lab, article, or local protocol.
ng/dL
Higher ARR values are more convincing when aldosterone is also high enough.
renin
This is the highest renin value you still want to count as suppressed.
Collection context
Tap the options that best match the blood draw.
Posture and timing
Ideal / morning
Not sure
Possibly non-ideal
Potassium corrected
Yes
Not sure
No
Interfering medications likely
No / held if needed
Not sure
Yes / possible
How to use this tool
  • Enter aldosterone and renin using the same method and units style as the lab report.
  • Choose PRA or direct renin first, because the ratio and cutoff logic can differ.
  • Use the assumptions tab to match the cutoff and renin suppression level you want to screen against.
Result logic used here
  • The calculator checks whether ARR meets your cutoff.
  • It also checks whether aldosterone clears your minimum and whether renin is still suppressed by your chosen threshold.
  • Collection context can strengthen or weaken confidence in the screen summary.
Important note
This is an educational screening aid and not a diagnosis. Positive screens often need clinician review and, in some settings, confirmatory testing.

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. Screening typically requires confirmatory testing and clinician interpretation.
  • 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 ≈ 0.03604 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).

\text{ARR} = \frac{A}{R} \\ \text{RAR} = \frac{R}{A} = \frac{1}{\text{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 the plasma renin activity (e.g., ng/(mL-h)). 

ARR is calculated by dividing aldosterone by plasma renin activity (ARR = A/R). 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, determine the plasma renin activity (R) from your lab report (e.g., ng/(mL-h)). 
  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