How to Delete a Gmail Account?
On your browser, type http://www.google.com. Click on the Gmail link on the top-left corner of the screen.
Sign-in with your Gmail ID and password. Make sure you type the entire Gmail address (E.g. email@example.com) while signing in.
Click on the Settings link on the top right corner of the screen.
Click on the Accounts and Import section just below the Settings title
Next, click on Google Account Settings in the Change Account Settings section.
In the My Products category, click on the Edit link.
Click on Remove Gmail Permanently just below the Delete a Product category.
Remember, once you have deleted your Gmail account, you won’t be able to access your email, send or receive any messages. You will also be unable to login with your deleted Gmail username in the future.
Your Gmail account won’t be removed quickly. It will take at least two business days to remove the Gmail account from the day of your request. Your mail will be closed and all its contents will be deleted permanently.
Click on the check box titled Yes, I want to permanently delete firstname.lastname@example.org and remove it from my Google Account.
Then, click on the Remove Gmail button. Now to you know how to delete a Gmail account. Make sure you delete those unused gmail accounts and not your primary Gmail account.