Yeast Conversion Calculator
Convert between active dry yeast, instant yeast, fresh cake yeast, and sourdough starter with precise ratios. Enter an amount in any unit and get the equivalent for your target yeast type, plus proofing instructions and water temperature guidance for perfect bread every time.
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Usage Tip
Instant yeast can be mixed directly into dry ingredients without proofing, saving time. It dissolves quickly and starts working immediately once liquid is added.
Quick Reference Table
| Active Dry | Instant | Fresh/Cake | Sourdough Starter |
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How Yeast Conversion Works
Different types of yeast have varying levels of potency because of how they are processed and their moisture content. Active dry yeast is the baseline for most conversions. Instant yeast is more concentrated and requires only 75 percent of the active dry amount because the smaller granules activate faster and more efficiently. Fresh cake yeast contains significantly more water, so you need roughly three times the weight of active dry yeast to achieve the same leavening power. Understanding these ratios ensures your bread rises properly regardless of which yeast type your recipe calls for or what you have on hand.
Sourdough starter conversion is less precise because wild yeast cultures vary in strength based on feeding schedule, age, and environment. A general guideline is to use roughly 100 grams of active starter (at 100 percent hydration) for every 7 grams of commercial yeast. When substituting sourdough starter, you also need to account for the flour and water it contains by reducing your recipe quantities accordingly. The rise time will be longer with sourdough starter compared to commercial yeast, typically requiring 4 to 12 hours depending on temperature and starter activity.
Yeast Types and Proofing Instructions
Active dry yeast must be dissolved in warm water (100-110°F or 38-43°C) for 5 to 10 minutes before use. You should see foamy bubbles form on the surface, which confirms the yeast is alive and active. If no foam appears after 10 minutes, the yeast is likely expired and should be discarded. Always check the expiration date on commercial yeast packages and store them in a cool, dry place or refrigerate after opening for maximum shelf life.
Instant yeast, also called rapid-rise or bread machine yeast, can be mixed directly into dry ingredients without proofing. It tolerates slightly higher water temperatures (120-130°F or 49-54°C) because it is not exposed to liquid alone. Fresh cake yeast should be crumbled and dissolved in lukewarm water (95°F or 35°C) before adding to dough. It is highly perishable and must be refrigerated, lasting only about two weeks after purchase. Sourdough starter requires regular feeding with equal parts flour and water to maintain an active, healthy culture capable of leavening bread.
Water Temperature Guide for Yeast
Water temperature is critical for yeast activation. Too cold and the yeast stays dormant; too hot and it dies. For active dry yeast, use water between 100-110°F (38-43°C) to dissolve and activate the granules. Instant yeast tolerates warmer liquid at 120-130°F (49-54°C) because it mixes with flour first, which buffers the heat. Fresh yeast is most sensitive and performs best with lukewarm water around 95°F (35°C). When using sourdough starter, room temperature water works well since the wild yeast is already active and does not need thermal activation.
A kitchen thermometer is the most reliable way to check water temperature. If you do not have one, test the water on the inside of your wrist — it should feel comfortably warm, similar to a warm bath. Water that feels hot to the touch is likely above 120°F and could kill active dry yeast or fresh yeast on contact. In cold environments, you may want to use slightly warmer water to compensate for heat loss when it contacts the flour and mixing bowl, which can cool the dough significantly during the initial mixing stage.
Frequently Asked Questions
How do I convert active dry yeast to instant yeast?
Multiply the active dry yeast amount by 0.75. For example, if your recipe calls for 7 grams of active dry yeast, use 5.25 grams of instant yeast. Instant yeast is more potent because its smaller granules dissolve and activate faster than active dry yeast.
How much fresh yeast equals one packet of active dry yeast?
One standard packet of active dry yeast (7 grams or 2.25 teaspoons) is equivalent to about 21 grams of fresh cake yeast. Fresh yeast contains more moisture, so you need approximately three times the weight to achieve the same leavening power.
Can I substitute sourdough starter for commercial yeast?
Yes. Use approximately 100 grams of active sourdough starter (at 100 percent hydration) to replace 7 grams of active dry yeast. Remember to reduce the flour and water in your recipe by about 50 grams each to account for what the starter contributes. Rise times will be significantly longer.
Does instant yeast need to be proofed in water?
No, instant yeast does not need proofing. It can be mixed directly into dry ingredients. The smaller granule size allows it to dissolve on contact with liquid in the dough. However, if you want to verify that your instant yeast is still active, you can proof it in warm water — it should foam within 5 minutes.
What happens if I use the wrong water temperature for yeast?
Water that is too hot (above 140°F or 60°C) will kill yeast cells permanently. Water that is too cold (below 80°F or 27°C) will leave yeast dormant and your dough will not rise properly. Active dry yeast needs 100-110°F (38-43°C), instant yeast tolerates 120-130°F (49-54°C), and fresh yeast prefers around 95°F (35°C).
How long does each type of yeast last?
Unopened active dry and instant yeast last up to 2 years stored in a cool, dry place. Once opened, they last 4-6 months in the refrigerator or up to a year in the freezer. Fresh cake yeast is highly perishable and lasts only 1-2 weeks in the refrigerator. Sourdough starter lasts indefinitely if fed regularly.