Sitticus Fasciger one source said about 1.5 mm
another source 3-4 millimeters (0.12 - 0.16 in).
This was in our bathroom sink, again spotted by Pam) all I can say it was small, tiny, tiny, and really does jump. It is hopefully waiting somewhere, still in our house, for it's next meal.
Don't like spiders but there is something about this little chap that is quite fascinating. Don't think I would like to come face to face with him though. The eyes are quite spooky. Great detailed shot.