Did you Know? Yeast Tutorial

Many recipes call for a packet of yeast rather than an actual measurement. If you buy your yeast and other baking supplies in bulk, as I do for maximum savings, then you need to know the actual amount of yeast to use rather than the generic 1/4 ounce packet of dry yeast.

So here's your answer, courtesy Red Star:

A 1/4 -ounce packet of active dry yeast contains approximately 2-1/2 teaspoons

Red Star has many other really great and useful pages on their site, including a yeast conversion chart:

Flour	Dry Yeast			Cake Yeast
cups*	packages (1/4 oz.)	grams	teaspoons	ounces
0 - 4	1	7	2+1/4	2/3
4 - 8	2	14	4+1/2	1+1/3
8 - 12	3	21	6+3/4	2
12-16	4	28	9	2+2/3
16-20	5	35	11+1/4	3+1/3

 * One pound of flour is approximately equal to 4 cups of flour.

If the ratio of sugar to flour is more than 1/2 cup sugar to 4 cups flour, an additional packet of yeast (2 1/4 tsp) per recipe is needed. An excessive amount of sugar slows down yeast fermentation.

When changing your bread recipe from cake yeast to dry yeast, any of the dry yeast types (Active Dry Yeast, Instant Yeast or Bread Machine Yeast) may be substituted.