Abstract: A company size estimation (CSE) system predicts employee number ranges for companies based on information available in open government and website sources. The CSE system breaks down the problem into two consecutive machine learning tasks. A first operation identifies large companies and a second operation identifies employee number ranges for small and medium-sized companies. Both operations take advantage of a rich set of firmographic attributes collected for companies, such as industry codes, office locations, corporate website text, website traffic, social media presence, and discoverability with respect to various data sources.