How this calculator works
An absolute reticulocyte count is a concentration, found by multiplying the red cell concentration by its reticulocyte fraction. It is distinct from a corrected reticulocyte percentage, which adjusts for the degree of anaemia using hematocrit. This page keeps those outputs separate. The optional correction uses a reference hematocrit you can change; it does not estimate the maturation factor needed for a production index. The result is an estimate for information only and is not medical advice.
Formula
Absolute reticulocytes (x 10^9/L) = RBC (x 10^12/L) x reticulocyte fraction x 1000. Corrected fraction = reticulocyte fraction x patient Hct / reference Hct.
Worked example
RBC 5 x 10^12/L and reticulocytes 2% give 100 x 10^9/L, or 100000 cells/µL. RBC 3 with 5% gives 150 x 10^9/L; at Hct 30% and reference 45%, the corrected percentage is 3.3333%.
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Frequently asked questions
Is hematocrit enough for an absolute count?
No. Hematocrit corrects a percentage, but a true absolute count requires the red cell concentration.
Why is there a factor of 1000?
The RBC input uses x 10^12/L while the absolute reticulocyte output uses x 10^9/L.
Is the corrected percentage the production index?
No. The production index also divides by a reticulocyte maturation factor.