It varies a lot based on the medium! If I'm writing a blog post, the research might only be a few hours -- I'm often writing on an area on which I already know a bunch, so I'm mostly doing research to catch me up to speed on recent events.

If I'm writing a shorter column -- like one of my 800-ish-word ones for Wired, or a 1,500-word one for Smithsonian, then it's usually about a week and a half to two weeks of research (reading, interviewing) before I write.

If it's a big feature article -- i.e. 4,000 to 8,000 words for Wired or the New York Times Magazine -- then it's a few months of research and reporting.

For a book, it's more like 1.5 to 2 years of research before the writing begins in earnest ...