The answer is between 34 to 203 beads, depending on the size of the beads of 2mm to 12 mm.
How big is a 2mm or 12mm beads? Well 2mm is tiny while 12mm is about the size of a peanut but this is only my guesstimate. To be exact, get the ruler or caliper.
Anyway, Szarka has a great article on the above at her site.
Head down to Magpie Gemstones and you shall find answers to these burning questions.
There are great conversion Charts by Dr. Karen Meador of Dreamcatcher Designs as well as Madeline Hoffman.
Here is a glimpse of the chart indicating the number of beads on a 16" Strand by Dr. Karen.
For bead strands of less than 16" i.e. 14" and 15", Madeline Hoffman has a chart workout for us.
For anything shorter, I guess we have to count manually....hehehe..just joking.
I actually do this sometimes...lol.
Thanks Szarka and Dr. Karen for sharing this informative article.