The easiest way to cross reference bearing part numbers is to use the manufacturer's website. Most major manufacturers provide a lookup service like the one at Timken.com, which searches and cross references parts by number and size.
If you can't locate the correct part, double check the manufacturer and be sure to use the correct manufacturer's website. Some manufacturers use different numbering systems, so parts made by one manufacturer may have a different number than the same part made by another manufacturer. These sites usually support partial searches as well. If your first search is unsuccessful, try again using only the first half of the serial number, or search by size instead.
Some manufacturers, such as NTN, also offer a search of competitors products and provide equivalent replacement parts. Always double check the exact specifications of parts when ordering replacements from a different manufacturer. It's easy to mix up parts when comparing them across manufacturers if they have different numbering and organization systems.
If the manufacturer's website does not provide a lookup service, find the most recent bearing interchange guide for that manufacturer and look up the part manually by serial number. Manufacturers use different numbering systems, but the first few pages of a guide often contain instructions on how to cross reference parts by hand.