Memory has become a critical parameter for many HEP applications and as a consequence some experiments had already to move from single- to multicore jobs. However in the case of LHC experiment software, benchmark studies have shown that many applications are able to run with a much lower memory footprint than what is actually allocated. In certain cases even half of the allocated memory being swapped out does not result in any runtime penalty. As a consequence many allocated objects are kept much longer in memory than needed and remain therefore unused. In order to identify and quantify such unusued (obsolete) memory, FOM-tools has been developed. The paper presents the functionalities of the tool and shows concrete examples on how FOM-tools helped to remove unusued memory allocations in HEP software.