If you've been using gMail for any length of time, then do yourself a favor and use the Find & merge duplicates feature. There is almost no risk now that Google's added the Restore contacts feature!
If you're an Android user, then you should get a double-win by condensing contacts in both places.
Step 1Click Contacts. Click More menu. Select Find & merge duplicates.
Click Merge button. You can click the expand link to see more details about the merges.