The formal organisation of the leidang, the ship-militia, is a little later than your period; but the ships probably did not change much even over two or three centuries, so we can take the leidang ship as a reasonable type example. Each ship-district, of which there were not quite 300 in Norway, had to supply a ship of "40 (later 24) oars", and probably the same number of crewmen. So, a typical Viking ship was between 20 and 40 men.

For a large ship, the Long Serpent, Olav Tryggvason's flagship and noted in saga as a particularly formidable vessel, was built with 34 "rooms", that is, pairs of oars - so it would have 68 crewmen, almost twice the size of a regular ship.

If you check the Icelandic sagas, you will see many instances of people going a-viking with one or two ships; but it is not clear whether this is typical of continental Scandinavia, which was much wealthier and also more centralised. When the kings of united Norway went out for war, they would call up several hundred ship-districts, in addition to ships privately outfitted by herser and jarls. When Harald Hardråde invaded England he is said to have had 300 ships, and his army is estimated at 9000 men - which incidentally gives us back the same 30 men per ship as above.