Convert between active dry yeast, instant yeast, fresh yeast, and sourdough starter amounts.
This tool converts a recipe's yeast across the four forms home bakers actually buy: active dry, instant, fresh cake, and sourdough starter. It applies the standard baker's ratios - instant is 25% stronger than active dry, fresh yeast outweighs both - and accepts either volume or weight. The thing most users get wrong: instant yeast is not a 1:1 swap for active dry, so substituting without converting over-leavens the dough and shortens the rise. The other surprise is the sourdough leg, which is a ballpark, not a measurement: starter strength swings with its hydration and activity.
A concrete input and expected output from the current implementation.
Input
2 teaspoons active dry yeast
Expected output
1.5 teaspoons instant yeast (about 4.5 g); about 14 g fresh yeast; roughly 3/4 to 1 cup of ripe 100% hydration sourdough starter
Instant yeast is about 25% stronger than active dry, so 2 teaspoons becomes 1.5 teaspoons (times 0.75), and at 3 g per teaspoon that is 4.5 g. Fresh yeast weighs roughly 2.5 times as much as active dry (5.6 g becomes about 14 g). The starter figure is the ballpark leg: a cup of ripe 100% hydration starter is the usual stand-in for a 2.25 teaspoon packet, so 2 teaspoons scales to just under a cup.
The dry-yeast leg runs on fixed factors: instant is 0.75 times the active-dry volume, or multiply instant by 1.25 to get active dry. Fresh yeast converts by weight only, about 3 times the instant weight and 2.5 times the active-dry weight. Standard teaspoon densities back the volume entries, 3 g per teaspoon of instant, so teaspoons, tablespoons, and grams all resolve to the same result.
Starter converts through its dry-yeast equivalent, assuming a ripe, 100% hydration starter: roughly one cup of starter stands in for a 2.25 teaspoon packet of yeast. Because starter is about half flour and half water and its activity swings day to day, the output is a starting point. Adding starter also changes the dough's flour, water, and rise time, which the ratio alone cannot capture.
No - use 25% less instant. A recipe's 2 teaspoons of active dry becomes 1.5 teaspoons of instant. The reverse also works: multiply instant by 1.25 for active dry. Either way, expect a slightly faster rise with instant, since it needs no dissolving and starts working immediately. Both can be mixed straight into the flour.
Yes, with two caveats. Starter is roughly half flour and half water, so trim the recipe's flour and liquid by about the weight of starter you add, and expect a slower, less predictable rise than commercial yeast gives. The converter's figure assumes a ripe, 100% hydration starter; a cold or runny one needs more time or more starter.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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