The actual Census test itself is a timed test, which takes thirty minutes. However, you will want to leave more time in your schedule than that. It can take up to one and a half hours to go through all of the preliminary tasks, such as filling out forms and going through the test procedure. Oftentimes others may have questions that need answering before taking the test, or there could be other delays coming up while filling out forms. So make sure you don’t go on a day where you need to be someplace else immediately after the test.
You would probably be wise to allow yourself two hours at the actual test location, and then factor in the amount of time it will take you to drive to and from the place the testing is taking place. Give yourself a little leeway for getting lost or in case the directions are inaccurate or incomplete. On the day I went to take the test, it wasn’t exactly clear where to go and I spent some time wandering around the Veterans Hospital looking for the correct room. No one who actually worked at the hospital had any idea what I was looking for and they had no knowledge that the Census jobs test was even being held in their building. But don’t be surprised by any of that! It is your typical federal bureocracy at work!
Also, before you head out to the testing location, it’s a good idea to take another look at the documention you are expected to bring with you. Check what you need to bring and double-check that you have both forms of ID with you before leaving home.