This Technical Memorandum provides a detailed and step-by- step method for determining uncertainty of certain calibration procedures common to instruments used in lumen measurement laboratories. This document uses the structure proposed in the Guide to the Expression of Uncertainty in Measurement (GUM) for its recommendations. For each calibration procedure presented in this document, a mathematical model is developed, estimates of each input quantity are discussed, and guidance is provided for the evaluation of the standard uncertainty of each input estimate. With this information, the combined standard uncertainty is calculated, effective degrees of freedom are calculated, and finally, the expanded uncertainty is reported.