According to jlptbootcamp's
annotated N1 practice test,
4 short passages (150-200 characters), 1 question each
3 medium-length passages (~500 characters, "roughly 3/4 of a page"), 3 questions each
1 long passage (~1000 characters), 4 questions
1 integrated comprehension: 2-3 passages on a topic, 3 questions about the "contrasts and similarities" of the passages.
1 thematic comprehension (~1000 characters) "typically essays or editorials about a particular topic", 4 questions.
1 information retrieval, 2 questions (no character count mentioned, but you don't have to read all of it anyway)
One of the passages will likely be written sideways (AFAIK only on the N1)
I'd estimate 5500 characters plus 26 questions and their answers, probably at least 100 characters per question. Plus the vocab and grammar sections, particularly word usage (6 questions, let's say 20+ characters per alternative) and sentence grammar (but you don't necessarily have to read the whole passage).
About 10000 characters in total. Some of which you will have to reread: to home in on the meaning of that one word you've never seen before that is key to the piece; to reread the relevant passage (or even the question) because you couldn't keep it in memory while reading the alternatives; to skim the passage over because they suddenly asked you about the author's
point after busying you with nitpicky details...
Of course, the simplest way to see if you're fast enough is to take a full-sized sample test such as the free
workbook.
Edited: 2014-10-01, 7:44 am