RBC Indices Calculator - MCV, MCH, and MCHC
Enter your hemoglobin, hematocrit, and red blood cell count to calculate all three core RBC indices: MCV (mean corpuscular volume), MCH (mean corpuscular hemoglobin), and MCHC (mean corpuscular hemoglobin concentration). Each result is compared against standard reference ranges and interpreted clinically so you can understand what the numbers mean, not just what they are.
Formula
Worked example
For a patient with Hgb 13.5 g/dL, Hct 40%, and RBC 4.5 x10^12/L: MCV = (40 / 4.5) x 10 = 88.9 fL (normocytic); MCH = (13.5 / 4.5) x 10 = 30.0 pg (normochromic); MCHC = (13.5 / 40) x 100 = 33.8 g/dL (normochromic). The Hgb/Hct ratio is 13.5/40 = 0.338, close to the expected 0.33.
What are RBC indices and why do they matter?
Red blood cell (RBC) indices are three calculated values that describe the size and hemoglobin content of your red blood cells. They are automatically derived from the hemoglobin, hematocrit, and RBC count on a routine complete blood count (CBC). Clinicians rely on RBC indices primarily to classify anemia, the condition in which blood carries insufficient oxygen. Rather than simply labeling anemia as present or absent, the indices pinpoint the morphological category - microcytic (small cells), normocytic (normal cells), or macrocytic (large cells) - which directly narrows the list of likely causes and guides further testing. MCV is generally considered the most diagnostically useful of the three, while MCH and MCHC provide supporting information and cross-checks.
What is MCHC and what does it tell you?
MCHC stands for Mean Corpuscular Hemoglobin Concentration. It measures how much hemoglobin is packed into each unit of red cell volume, expressed in grams per deciliter (g/dL). The formula is: MCHC = (Hemoglobin [g/dL] / Hematocrit [%]) x 100. The normal range is roughly 32-36 g/dL. A low MCHC (below 32 g/dL) indicates hypochromia - cells that appear pale under the microscope because they are under-filled with hemoglobin. This is characteristic of iron deficiency anemia and thalassemia. A high MCHC above 36 g/dL is uncommon and diagnostically important: it is the hallmark of hereditary spherocytosis, a condition in which abnormally shaped cells pack more hemoglobin per unit volume. An elevated MCHC can also signal severe burns or be an artifact caused by hemolysis, lipemia, or an elevated bilirubin in the blood sample. Importantly, MCHC closely tracks with MCV in most anemias: low MCV + low MCHC together strongly suggest iron deficiency, while a normal MCV with a low MCHC is unusual and warrants a careful look at the blood smear.
MCV and MCH: the other two indices explained
MCV (Mean Corpuscular Volume) is the average volume of a single red blood cell, measured in femtoliters (fL, or 10^-15 L). The formula is: MCV = (Hct [%] / RBC [x10^12/L]) x 10. Normal is 80-100 fL. Values below 80 fL define microcytosis, most commonly due to iron deficiency, thalassemia, or anemia of chronic disease. Values above 100 fL define macrocytosis, most often caused by vitamin B12 deficiency, folate deficiency, liver disease, or alcohol use. MCV is typically the first index a clinician checks when investigating anemia, because the size category immediately partitions the differential diagnosis. MCH (Mean Corpuscular Hemoglobin) is the average mass of hemoglobin in a single red cell, measured in picograms (pg). Formula: MCH = (Hgb [g/dL] / RBC [x10^12/L]) x 10. Normal is 27-33 pg. MCH tends to parallel MCV - small cells generally carry less hemoglobin (low MCH) and large cells carry more (high MCH). The Hgb-to-Hct ratio provides a quick cross-check: in healthy blood it is close to 0.33, meaning hemoglobin in g/dL is roughly one-third the hematocrit percentage.
Anemia classification using RBC indices
RBC indices allow anemia to be classified into three broad morphological categories, each with its own set of likely causes. Microcytic anemia (MCV below 80 fL, often with low MCH and low MCHC): the most common cause worldwide is iron deficiency, followed by thalassemia trait or disease, anemia of chronic disease, and lead poisoning. Sideroblastic anemia is a rarer cause. Normocytic anemia (MCV 80-100 fL): suggests acute blood loss, hemolytic anemia, anemia of chronic inflammation or kidney disease, early iron or B12 deficiency (before cells have had time to change size), or bone marrow failure. Macrocytic anemia (MCV above 100 fL): vitamin B12 or folate deficiency is the most important cause to identify because it is treatable and, if from B12 deficiency, can cause irreversible neurological damage if missed. Other causes include liver disease, hypothyroidism, alcoholism, and myelodysplastic syndrome. Certain drugs (methotrexate, hydroxyurea, azathioprine) also raise MCV. The morphological classification does not confirm a diagnosis on its own - additional tests such as serum ferritin, serum iron, transferrin saturation, reticulocyte count, peripheral blood smear, and serum B12 or folate levels are usually needed to reach a definitive answer.
RBC indices reference ranges and interpretation
| Index | Low (abnormal) | Normal range | High (abnormal) | What it measures |
|---|---|---|---|---|
| MCV | < 80 fL (microcytic) | 80-100 fL | > 100 fL (macrocytic) | Average red cell size |
| MCH | < 27 pg (hypochromic) | 27-33 pg | > 33 pg (macrocytic pattern) | Avg hemoglobin mass per cell |
| MCHC | < 32 g/dL (hypochromic) | 32-36 g/dL | > 36 g/dL (spherocytosis risk) | Hemoglobin conc. per cell volume |
Ranges reflect commonly cited adult laboratory values. Individual lab reference intervals may differ slightly.
Frequently asked questions
What is MCHC in a blood test?
MCHC stands for Mean Corpuscular Hemoglobin Concentration. It is a calculated value from your complete blood count (CBC) that expresses how much hemoglobin is present per unit volume of red blood cells. A normal MCHC is 32-36 g/dL. A low MCHC indicates hypochromic (pale) red cells, most often caused by iron deficiency. A high MCHC above 36 g/dL is uncommon and is classically associated with hereditary spherocytosis. The formula is: MCHC = (Hemoglobin [g/dL] / Hematocrit [%]) x 100.
What does a low MCV mean?
A low MCV (below 80 fL) means your red blood cells are smaller than normal, a condition called microcytosis. The most common cause is iron deficiency anemia, which is also the most common cause of anemia globally. Other causes include thalassemia (a genetic hemoglobin disorder), anemia of chronic disease, lead poisoning, and sideroblastic anemia. A low MCV is usually accompanied by a low MCH and, in iron deficiency, a low MCHC as well.
What does a high MCV mean?
A high MCV (above 100 fL) means your red blood cells are larger than normal, called macrocytosis. The most clinically important cause is vitamin B12 or folate deficiency, because both are treatable and B12 deficiency in particular can cause irreversible nerve damage if left untreated. Other causes include liver disease, alcoholism, hypothyroidism, and certain medications such as methotrexate, hydroxyurea, or azathioprine. A high MCV is often found alongside a high MCH.
How is MCH different from MCHC?
MCH (Mean Corpuscular Hemoglobin) measures the average absolute mass of hemoglobin in a single red cell, expressed in picograms (pg). MCHC (Mean Corpuscular Hemoglobin Concentration) measures the average concentration of hemoglobin within a unit volume of packed red cells, expressed in g/dL. Think of MCH as the total amount of hemoglobin per cell and MCHC as how densely packed that hemoglobin is relative to cell volume. Both can be low in iron deficiency (small, pale cells), but MCHC is the more specific marker for color intensity of the cells, and a high MCHC has a different clinical meaning from a high MCH.
Can RBC indices diagnose anemia on their own?
No. RBC indices classify the morphological type of anemia (microcytic, normocytic, or macrocytic) but cannot diagnose the underlying cause by themselves. A definitive diagnosis almost always requires additional tests: serum ferritin and iron studies for suspected iron deficiency, serum B12 and folate for macrocytic anemia, hemoglobin electrophoresis for thalassemia, and a reticulocyte count and peripheral blood smear to evaluate red cell production and morphology in more detail. Always discuss your results with a healthcare provider.
What is a normal MCHC level?
The normal range for MCHC in adults is 32-36 g/dL in most clinical laboratories, though some set the upper limit at 35 or 35.5 g/dL. Values below 32 g/dL are classified as hypochromic and are most commonly seen in iron deficiency anemia. Values above 36 g/dL are hyperchromic and are the hallmark of hereditary spherocytosis. Reference ranges can vary slightly between laboratories, so always compare your result to the reference interval printed on your own report.
What does the Hgb-to-Hct ratio of 0.33 mean?
In healthy individuals, the hemoglobin value in g/dL is approximately one-third of the hematocrit percentage. This 0.33 ratio is a built-in cross-check: since MCHC = (Hgb / Hct) x 100, and the normal MCHC is about 33-34 g/dL, a ratio of 0.33 is simply another way to express a normal MCHC. If the ratio is significantly outside this range, it may flag a transcription error in the values or a sample quality issue (such as hemolysis or lipemia) that has artificially altered one of the measured values.