How to Sync all contacts to Gmail?
Go to Settings > Accounts > Google > Make sure that sync is turned on for your Gmail Account.
Once Sync is turned on. Google will try to sync your phone contacts to Gmail and Gmail contacts to phone. But it will only sync the Gmail contacts to phone. Now here is Why: You have saved all your contacts in the phone as ‘Phone Contacts’ not as ‘Gmail Contacts’ or Google Contacts.
Now you want to sync all your phone contacts to Gmail. The procedure is damn easy for KitKat and Lollipop devices.
Devices running Android KitKat and Lollipop.
Go to Contacts > Options…