I actually timed myself and found that one line of dialogue (i.e. the equivalent of each text-box click) is on average 16.5 words, and it takes around 2.5 seconds to read through. If it is voiced, then it can take up to 5 seconds.mrsulu wrote:VNs seem to be counted either in length-to-ending or length-to-seeing-all-endings (or at least I'm-done). I'd imagine "lines" being a pretty straightforward calculation---10-15 seconds per line. Then you find your longest path, add some rule of thumb (say, 25-50% of that per major branch in your story) and you've got some idea of length.
Designing for the speed reader in mind helped me to make sure that there is enough content. Adding more choices than there are actual story paths helps to add reading time while making the filler text less obvious...instead, it flushes out the experience more.