Converting stand mixing time to hand mixing
I remember when cake mixes included the number of strokes needed to mix the batter by hand.  The Betty Crocker FAQ website (a U.S. baking mix company) suggests 150 strokes per each minute of electric mixer time recommended.  Note: that is not 150 strokes per minute!  So if the directions call for 2 minutes of mixing, that translates to 300 strokes.

Betty Crocker FAQ Site

EDIT

The stroke count in this answer is specifically for use with a cake mix.  As KatieK pointed out, mixing time and strokes are really dependent on the ingredients and desired consistency for that particular recipe and step in the recipe.