At the time of writing, Facebook doesn’t allows you to download all your friends’ contact details. So its very hard to export Facebook contacts and import it to Gmail.
However, then is a workaround using which you can easily import Facebook contacts to Gmail. Here’s the procedure:
First import all your Facebook contacts to your Yahoo mail account. Go to the Contacts tabs near the Mail tab in your Yahoo Mail, and click on Popular Tools. Here, choose “Import your contacts from other accounts to Yahoo”
Click on Facebook. Click Allow when the application access window open on Facebook. Once you do this, the import process will start.
After that, all the contact details of your Facebook friends will be in your Yahoo account.
Now to import all these contacts in Gmail, first export your address book in a CSV format from your Yahoo account. To do this, click on Accounts, and click Export. Select Yahoo! CSV and you will get all contact details in CSV format.
Now, open Gmail and click on Contacts .
Upload the CSV file downloaded form Yahoo Mail here. That’s it. You have all your Facebook contacts imported to Gmail now.