Engineers Edge, Eglin Fasteners Group and Laptop Screws are some of the places where you can find metric bolt specifications charts. These sites provide detailed information on general and specific metric bolt grades.
Engineers Edge features standardized ISO specifications table charts. The site gives various links that provide specification charts for different bolt designs, fasteners and screws.
Eglin Fasteners Group gives metric bolt conversion data for industrial bolts, machine screws and small diameter screws. The charts on this site provide metric bolt conversions and DIN numbers for fasteners.
Laptop Screws provides metric conversion charts for metric-to-inch screw threads. The site features hundreds of bolt sizes with screw assortments for easy conversions. The site allows you to use its menu in your metric bolt conversions.