Reticulocyte Production Index Calculator

Enter reticulocyte percentage, hematocrit, and maturation factor to compute the RPI and interpret bone marrow adequacy in anemia.

Lab Values

Normal adult range: 0.5% – 1.5%

Normal: ~45% (male), ~40% (female)

Leave on "Auto" to have the calculator choose for you.

Enter lab values and click Calculate RPI to see results.

RPI Interpretation Reference

RPI Interpretation Typical Causes
< 2 Inadequate (hypoproliferative) Iron deficiency, chronic disease, aplastic anemia, renal failure
2 – 3 Borderline / adequate Early treatment response, mixed picture
> 3 Adequate (hyperproliferative) Hemolytic anemia, acute blood loss with intact marrow

Maturation Time Reference

Hematocrit Maturation Time
≥ 40%1.0 day
30% – 39%1.5 days
20% – 29%2.0 days
< 20%2.5 days

Summary

Enter reticulocyte percentage, hematocrit, and maturation factor to compute the RPI and interpret bone marrow adequacy in anemia.

How it works

  1. Enter the patient's reticulocyte percentage from a CBC (complete blood count).
  2. Enter the patient's hematocrit (Hct) as a percentage.
  3. The tool auto-selects maturation time based on Hct, or you can override it manually.
  4. Corrected Reticulocyte Count (CRC) = Reticulocyte% × (Hct ÷ 45).
  5. RPI = CRC ÷ Maturation Time.
  6. An RPI ≥ 2 indicates an adequate marrow response; RPI < 2 indicates hypoproliferative anemia.

Use cases

  • Differentiating hypoproliferative from hyperproliferative anemia at the bedside.
  • Evaluating bone marrow response in iron deficiency anemia workup.
  • Assessing erythropoietic adequacy in chronic kidney disease or anemia of inflammation.
  • Monitoring treatment response in hemolytic anemia or after acute blood loss.
  • Medical education and clinical review of CBC interpretation.
  • Quick lab interpretation during hematology or internal medicine rounds.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu