You should multiply with 3 or 4, depending on your systems specs and the number of effects etc that is in your project. So a 30' movie may take up to 2 hours to render. This is important stuff if you have a deadline!
Many factors contribute: processor speed, frame size, frame rate, source media type, output format, frame size, effects added, transitions, color corrections, text, track motion, pan/crop, compositing, masking, layers, number of tracks, 3D motion .... and so on.
What's a normal rendering time to render a one hour project? Probably anywhere from 10 minutes to 10 days is completely normal.