It is really tough when you are handling hundreds of contacts in your mailbox. This situation becomes worst when your contacts are having duplicates. :(

Google has found the solution in Gmail for this kind of problem. Managing a big address book can be a challenge, so it’s no surprise that the top request for Google contacts is a fast, easy way to merge duplicate contacts. You’ve been able to merge contacts one-by-one for a while, but now we’ve added a single button that merges all your duplicate contacts at once. To clean up your contact list in one fell swoop, just click the “Find duplicates” button in the contact manager, review the merge suggestions (and uncheck any suggestions you don’t want merged), and hit the “Merge” button.