1 envelope (or package) of Active Dry Yeast, Instant Yeast, Rapid Rise Yeast, Fast Rising Yeast, or Bread Machine Yeast weighs 7 grams (quarter ounce) and equals 2 1/4 teaspoons (11 mL). This amount can be multiplied by the number of packages needed to make enough dough for one loaf of bread. The total cost of yeast is $0.75 per package. Envelopes of yeast are on sale at some grocery stores and warehouse clubs for as low as $0.50 each; others sell for $1.00 or more. The actual price of yeast varies depending on how many packages are used and when they are used. Regular prices are about $0.45 for a quarter-ounce packet and $1.25 for a half-ounce packet. However, yeasts can sometimes be found for less than $0.50 each if you shop around. Yeasts are the leavening agents that produce carbon dioxide gas that causes bread to rise. There are two types of yeast: instant and active dry. Instant yeast requires no further treatment after it has been mixed with water; it begins rising immediately. Active dry yeast needs to be activated first by mixing it with water until it is dissolved. Then the mixture should be allowed to sit for 10 minutes before using it to leaven your bread.