Abstract Systems engineers need quantifiable metrics for measuring the readiness of a system. The recently developed System Readiness Level ( SRL ) is such a metric. SRL is a function of Technology Readiness Level (TRL) and Integration Readiness Level (IRL). The mathematical operations used to define this function have some inherent properties. Four desired mathematical properties of SRL models are developed from these inherent properties and other properties suggested from a review of the literature. Matrix algebra and tropical algebra are discussed in the literature as possible mathematical operations. These mathematical operations are reviewed to determine if they meet the desired properties. Tropical Algebra (TA) is found to inherently meet these desired properties. Future research will be conducted to determine if an SRL model using TA is a viable option. ©2012 Wiley Periodicals, Inc. Syst Eng 16: