Here is the formula we use for percent recovery for frozen red cells. I could use the same formula, but I do not want to use HCT for LR. I want to know where the .0693 comes from in my density formula. It was established by the Freezing Protocol, FDA does not have a problem with it. I am training someone and he asked where the number comes from. I can't explain it. Do you know? Pre-GlycerolizationDeglycerolizationWeight266371Hematocrit7549Density1.0569751.038957RBC Concentration251.66357.09RBC Volume188.75174.97Percent Recovery92.70% Use HCT in decimal format. Use 75% for the pre-glycerolization HCT.Density (calculation = (0.0693 * HCT)+1.005)RBC Concentration = (Net Weight/Density)RBC Volume = (RBC Concentration * HCT)Percent Recovery = (Deglycerolization Volume/Preglycerolization Volume)