Hematocrit to Hemoglobin Ratio Calculator
Enter your hemoglobin and hematocrit lab values to calculate their ratio and compare it against the commonly used ‘rule of three’ reference.
The hematocrit-to-hemoglobin ‘rule of three’
In most people with normal red blood cells, hematocrit (the percentage of blood volume made up of red blood cells) is roughly three times the hemoglobin value (the protein that carries oxygen, measured in g/dL). This is often called the ‘rule of three’ and is used as a quick sanity check on paired lab results.
How this calculator works
Enter your hemoglobin and hematocrit values from a lab report, and this tool divides hematocrit by hemoglobin to get the ratio, then compares it to the typical range of about 2.8 to 3.2. A ratio noticeably outside that range can occur with certain red blood cell shape or size changes, but it can also simply reflect normal lab variation.
This calculator is for general educational reference only. It does not diagnose any condition, and any concerns about your lab results should be discussed with a qualified healthcare professional who has your full clinical picture.