Free · Laboratory measurement indices

Mentzer Red Cell Measurement Index

Divide mean corpuscular volume by the numerical red-cell count and retain the historical threshold context.

Formula & worked example
Private in your browser
No signup

Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Health results are educational estimates, not a diagnosis or treatment recommendation. A qualified clinician can interpret measurements in the context of your health.

Formula and method

MCV 60 fL and RBC 5 million/µL give index 12.

Mentzer index = MCV in fL / RBC count in millions per microliter.

Worked example

Enter these known values and leave the other values blank.

Mean corpuscular volume (MCV): 60 fl
Red blood cell count (RBC): 5 million/ mm³

Mentzer index: 12

Assumptions and limitations

MCV is entered in femtoliters and RBC as the numerical count in millions per microliter (equivalently 10¹²/L or millions per mm³). Enter 5 for 5 million/µL, not 5,000,000.
The index was proposed in 1973 for differentiating iron deficiency from thalassemia trait. A 2024 primary study in Saudi children with microcytosis found limited diagnostic accuracy; applicability and performance vary by population. Equality at 13 does not imply equal probability.
Positive measurements are required. Inverses preserve the stated numerical relationship and do not replace measured laboratory results.

Common questions

Which RBC number should I enter?

Enter the number in millions per microliter, such as 5 for 5 million/µL, with MCV in fL.

Can an index below 13 diagnose thalassemia?

No. It is a historical screening pattern with imperfect population-dependent accuracy. Laboratory confirmation and clinical assessment are needed.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

Explore laboratory measurement indices or browse all health calculators.