Microsoft has a handy utility that rates your passwords. It doesn’t just look at the length of the password, it looks at how you mix upper case with lower case letters, numbers, punctuation marks etc.
When creating new passwords for your online services aim for Good or Best.
Note: there might be better password checkers in existence, I suggest this one because it’s hosted on Microsoft’s site. Whether you love them or hate them I believe their intentions are good and they won’t try to steal passwords.