1. A computer system for building an inventory database, the computer system comprising: an electronic memory storage configured to store modules; a computer processor configured to execute the modules comprising at least: a data access module configured to access inventory data for a plurality of products from at least one inventory data source, a metadata extractor module configured to extract stated metadata from the inventory data for each of the plurality of products, a product evaluator module configured to determine a product category or a product identification based on the stated metadata for each of the plurality of products, a comparator module configured to compare for each of the plurality of products the product category or the product identification to stored metadata in a metadata database, wherein the metadata database comprises additional metadata for a plurality of products, a metadata identifier module configured to identify derived metadata for each of the plurality of products based on the comparison, wherein the derived metadata is metadata that is not stated metadata and is in the metadata database, a conversions module configured to generate a specific conversion rate for each of the plurality of products based on inputting the stated metadata and the derived metadata into a conversion rate formula, wherein the conversion rate formula is based on a linear or logistic regression analysis, a conversion rate assignor module configured to assign the specific conversion rate corresponding to each of the plurality of products, and a storage module configured to store in the inventory database for each of the plurality of products the stated metadata, the derived metadata, and the specific conversion rate.