This page is meant to be a tool for mass spectrometry. The formula masses for over 400 million formulas have been calculated and stored. Because of the large combinatorial problem, formulas with natural abundance masses less than 2000 daltons were calculated and heuristic rules were used to limit the formulas to those that are most likely to be found in nature. These rules were obtained from the paper by Kind and Fiehn, "Seven Golden Rules for heuristic filtering of molecular formulas obtained by accurate mass spectrometry" (Kind T. and Fiehn O. BMC Bioinformatics. 2007 Mar 27;8:105)
Please take a moment to review the input formats.
Because of the large file sizes and http post constraints, limit your query list to 500 entries or less. Very large files do not get transferred.
The results of your query will be deposited into a downloadable, tab seperated file and posted below. Please be aware that large queries may take some time to complete.