Lean manufacturing is a competitive philosophy adopted by many companies to produce cost effective products and services. Contemporary lean assessment tools are designed to evaluate a company's status of lean implementation and success. However, most lean assessment tools provide qualitative analysis and do not provide any clear direction of where the improvement efforts should be directed. In this paper, we propose a complementary methodology to assist contemporary lean assessment tools that will provide a quantitative measure of leanness by benchmarking other exemplar lean industries along with specific pointers for improvements based on cost considerations. The proposed Mahalanobis Taguchi Gram Schmidt System (MTGS) based methodology consists of four steps. The first three steps consist of data collection using contemporary lean assessment tools, standardizing the data, and using the standardized data for calculating the Mahalanobis Distance (MD) by the using the MTGS method. The MTGS method provides the direction of abnormality and can be used even in cases of multi-collinear data. The fourth step helps to identify the direction of improvement for a given set of capital constraints. The methodology is demonstrated using an example.