I came across this site that gives an estimate of how long it might take a hacker to guess your passwords using a ‘brute-force’ (dictionary) attack. While the actual time estimates are probably unreliable, it will give you an idea of the relative strength of your passwords. You will get an idea of the effect of including upper and lower case letters, numbers and symbols. Type your proposed password into the form to obtain the estimate.
I have checked the source code of this site and I am satisfied that the calculation is done in your browser using JavaScript code from Google Analytics: your password is NOT uploaded to any server, so you are not at risk by using this site (provided that the computer you are using is not already compromised).
