When Facebook was founded, every user was given an ID number. It began with ID #0, which redirects every user to their own profile page.
ID numbers 1-3 were tests that Mark Zuckerberg used to initially test Facebook; the profile pages no longer exist.
The first real Facebook user starts at ID #4. It belongs to Mark Zuckerberg.
Facebook ID numbers were assigned in somewhat sequential order; schools were chunked up in blocks up to 100,000 IDs. Harvard was the first chunk (0-99,999).
My number is about 5,500,000. This makes sense because Syracuse was the 56th school on Facebook.
It's not clear how IDs were assigned once Facebook expanded beyond college networks.
But, if you were an early Facebook member and joined through a university network, your ID number probably closely resembles the order in which you signed up for the site.
To find this number, look at your Facebook profile page. Assuming you didn't opt to change the url a few years back, it will be followed by a long string of numbers:
http://www.facebook.com /profile.php?id=5500958
That number, i.e. 5500958, is it.
Another really easy way to find it is FindMyFacebookID.com, and dump in your URL.
If you want to find it on your own and you already changed your URL to your name, that's easy too.
Go to your Facebook profile. Look at the top of your browser (Chrome, Firefox, etc) and to go "View" then "View Source" from the drop-down.
Search the page (hold down "Command" and "F" on a Mac) for "profile_id="
A few results will pop up, and all of them should be followed by a long string of numbers, such as "5500958."
That long string of numbers is your account number.
To confirm it, go to your web browser and type in the following url: http://graph.facebook.com/YOURNUMBER
It should churn out a result that looks like this, with your name:
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