There are online tools you can use to determine this.
A google search for “How long did my site take to load?” actually gives you one of the best ones as the first result:
http://tools.pingdom.com/
Sometimes it’s your host, sometimes it’s your isp, sometimes it’s the network in general. But run that test, pay attention to the waterfall, and deal with those items that take forever to load. Sometimes it’s only one or two things.
Moved to Support.