How to Proof Yeast

Test Your Yeast to See If It's Still Good

Mixing yeast and water, preparing dough
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It's a real bummer when a bread recipe fails to rise because it means you've wasted both time and ingredients. Fortunately, you can avoid this mishap by proofing your yeast before you use it.

What's Proofing?

Proofing means testing your yeast to see that it's still alive and able to start the fermentation process that will create the bubbles of gas that cause bread and other baked goods to rise. Yeast is a living organism. If it is near its expiration date, or it hasn't been kept in ideal conditions, there may not be enough living yeast cells to create the gas needed to make your bread rise.​

If you're an occasional baker, it's smart to test your yeast before you use it to make sure it's still fresh.

Do All Kinds of Yeast Need to Be Proofed?

No, the two kinds of yeast you may want to proof are active dry yeast and fresh active yeast (also called compressed yeast or cake yeast). You shouldn't proof RapidRise yeast, instant yeast or bread machine yeast. Those will lose their fast-rising ability if you proof them by dissolving them in liquid.

If you're a frequent baker, and your yeast isn't approaching its expiration date, you can probably get by without proofing your yeast. However, if you haven't used your yeast in a while, it's definitely worth delaying the start of your recipe by 10 minutes to make sure your yeast is still going to do its job.

What You Need to Proof Yeast

  • Yeast
  • Warm water: It should feel lukewarm. You may want to measure its temperature to ensure it is between 100 and 110 degrees F (40 degrees C). If the water is too hot, it'll kill your yeast.
  • Sugar
  • A bowl or one-cup liquid measuring cup

Instructions for Proofing Yeast

First, check for the amount of water and sugar called for in the recipe. You will be using one-quarter cup of water and one teaspoon of sugar to proof one packet of yeast (about 2-1/4 teaspoons). After proofing, you can add your yeast mixture to your recipe and adjust the amount of water and sugar needed accordingly. If your recipe doesn't call for sugar, add a small amount (1/8 teaspoon will do it), to give the yeast something to feed on.

Alternatively, if you have bought dry active yeast in bulk, you could proof the yeast to show the whole container is still active, and proceed with the recipe according to its instructions, rather than using the proofed yeast.

Combine the yeast, warm water, and sugar in a bowl or one-cup liquid measuring cup. Let it sit for 10 minutes. During this time, if the yeast is alive, it will start eating the sugar and fermenting it into alcohol and carbon dioxide.

After 10 minutes, you should see the yeast foaming up in the measuring cup to the half-cup line (doubling its height). If you used a bowl, you should see plenty of foam. If so, add the yeast mixture to the rest of your ingredients, and continue with the rest of your recipe.

If the mixture isn't bubbly, your yeast is no longer good. Dump out your mix, and start with fresh yeast. Unfortunately, there's no way to revive old yeast.


  • Dry active yeast usually has a shelf life of around 12 months. Once you open it, it's best to store it in the refrigerator. This will prolong its life. If you don't bake often, or you just want to keep your yeast fresh as long as possible, store it in the freezer. This will keep it fresh indefinitely. There's no need to thaw your yeast before you use it.
  • Be sure to check the expiration date before you buy your yeast.​​​ Unless you're a prolific baker, you probably won't be able to use up an older jar before it goes bad.
  • Store your yeast in an air-tight container, so it isn't inadvertently exposed to humidity or moisture that might activate it prematurely. Bulk yeast often comes in a vacuum-sealed foil pouch. If this is the way you buy your yeast, it's best to move it to a container that can be sealed tightly. This will help to keep it fresh and avoid messy spills.