Nymex Holdings, the parent company of the New York Mercantile Exchange, has increased the size and price range of its initial public offering in anticipation of strong investor appetite as US exchange stocks hit new highs.

Nymex is now planning to sell 6.5 million shares and has increased the price range to between $54 and $57, according to a regulatory filing with the Securities and Exchange Commission. Should the deal price at the top of the new range, the exchange could raise $370.5m (€288.2m), an increase of 19% on its previous estimate.