Yeast Conversion Calculator

The four types of yeast

All baker's yeast is the same organism.Saccharomyces cerevisiae.processed differently. The differences in form affect how you use them, not the flavour of the final bread.

Active dry yeast is dried and granulated with a partially dormant outer shell. It needs to be dissolved in warm water before use (proofing). It's the most common form sold in supermarkets and comes in 7g (¼ oz) packets.a convenient standard unit for home bakers.

Instant yeast (also fast-action, rapid-rise, or bread machine yeast) is finer-grained and fully active without proofing. It can be mixed directly into dry ingredients. It's about 25% more potent by weight than active dry, so you use less.

Fresh yeast (cake yeast, compressed yeast) is wet and unpasteurised.highest leavening power, shortest shelf life. Rarely found in supermarkets. Used extensively by professional bakers because it's cheaper at scale and some argue it produces better flavour.

Sourdough starter is a living culture of wild yeast and bacteria maintained through regular feeding. It leavens more slowly and less predictably than commercial yeast.but that unpredictability is the point. Flavour complexity, not pure leavening efficiency, is why bakers use it.

Conversion ratios explained

The conversion ratios used by this calculator:

Active dry to instant: multiply by 0.75. Instant yeast is roughly 25% more potent by weight, so you use 75% of the active dry amount. This is the most consistent conversion in baking. These two yeasts are interchangeable with only this adjustment.

Active dry to fresh: multiply by 3. Fresh yeast is about one-third as concentrated as active dry because it retains most of its water. Three times the weight delivers the same leavening power. Fresh yeast also dissolves without proofing. Crumble it into warm water or directly into the dough.

Active dry to sourdough starter: 1g active dry equals approximately 120g starter at 100% hydration. Important: when you substitute starter, you're adding flour and water (the starter itself is roughly 50% each). Adjust your recipe water and flour accordingly to keep the total hydration correct. Our yeast-to-sourdough converter handles this automatically.

Yeast to sourdough starter

The sourdough equivalence is the most asked-about conversion and the least reliably answered. Every source gives a different number because starter activity genuinely varies. Culture age, feeding schedule, flour type, and feeding recency all affect it.

The commonly cited range is 100–150g of active 100% hydration starter per 1g of active dry yeast. This calculator uses 120g as the midpoint. If your starter is very active and recently fed, lean towards 100g. If it's older or you keep it in the fridge, lean towards 150g.

This ratio doesn't account for extended fermentation time with sourdough. Commercial yeast works in 1–2 hours. Sourdough typically needs 4–12 hours of bulk fermentation depending on temperature and inoculation rate. You're not just swapping an ingredient. You're changing the timeline of the entire bake.

Instant vs. active dry.what actually differs

Both are Saccharomyces cerevisiae, dried. The manufacturing difference is the granule size and the drying temperature. Instant yeast is dried at lower heat, preserving more active cells, and ground finer so it hydrates without a proofing step.

In practice: instant is more convenient and slightly more reliable. Active dry has a longer shelf life and is more widely available. Both produce identical bread if used correctly. The flavour difference, if any, is imperceptible.

One important caveat: if your active dry yeast is old, proofing matters. Dissolve it in 38–43°C (100–110°F) water for 5–10 minutes before adding to your dough. If it foams, it's active. If it doesn't, it's dead.and no amount of kneading will save the bake.

Working with fresh yeast

Fresh yeast has a shelf life of 2–3 weeks refrigerated, sometimes up to 4 weeks if kept very cold and tightly wrapped. Signs it's still good: creamy beige colour, fresh bread smell, crumbles cleanly. Signs it's gone: grey or brown spots, slimy texture, sour smell.

You can freeze fresh yeast for up to 3 months. Crumble it into small pieces before freezing so you can measure what you need without thawing the whole block. Thaw in the fridge overnight before using.

Fresh yeast is hard to find in North American supermarkets but common in European ones. If a recipe from a European cookbook calls for it and you can only find active dry, multiply the fresh yeast quantity by 0.33 (or divide by 3) to get the active dry equivalent. This calculator does that automatically.

Standard packet reference

One standard US packet of active dry or instant yeast is 7g (¼ oz, approximately 2¼ teaspoons). This is calibrated to leaven one standard batch of bread dough using 3–4 cups (360–480g) of flour.

One 7g packet of active dry yeast converts to approximately 5.25g of instant yeast, 21g of fresh yeast, and 840g of active sourdough starter. These are the numbers to keep in your back pocket when a recipe refers to a “packet” and you're using a different format.