Yeast Converter

Background.

Baker's yeast is one organism, Saccharomyces cerevisiae, sold in three forms that differ mainly in how much water they hold. Fresh yeast — compressed, or cake yeast — is a moist, crumbly block that has to be refrigerated and keeps for days to weeks. Active dry yeast is dried into coarse granules that were traditionally dissolved in warm water before use. Instant yeast, also sold as rapid-rise or bread-machine yeast, is dried in finer particles that can go straight into the flour.

Because fresh yeast is mostly water, it takes more of it by weight to do the same work. Red Star, which makes all three, puts the exchange at one 2-ounce cake of fresh yeast for three quarter-ounce packets of dry, and gives the weight of a third of a cake as 18.9 g against a 7 g packet. That is a factor of 2.7: multiply dry yeast by 2.7 to get fresh, divide fresh by 2.7 to get dry. Between active dry and instant, the calculator swaps gram for gram, as Red Star and King Arthur Baking both advise.

Going from fresh to dry has a second step that most charts leave out. The water that was in the fresh yeast leaves the dough with it, and Lesaffre's guidance for bakers replacing compressed yeast with its SAF-Instant is to add extra water of about twice the weight of the dry yeast. The calculator reports that amount.

It also answers a separate question: how much yeast the recipe's flour needs. Red Star's chart gives one packet for up to 4 cups of flour, stepping up a packet for every further 4 cups, plus one more for a sweet dough.

What is yeast converter?

A yeast conversion finds the weight of one form of baker's yeast that gives the same leavening as a given weight of another. All the figures here are by weight, because a teaspoon of fine instant granules, a teaspoon of coarser active dry and a crumbled lump of fresh yeast do not hold comparable amounts. Red Star defines its packet as 1/4 oz, 7 g or 2 1/4 teaspoons, and its fresh yeast in 2 oz cakes, a 1 lb block being cut into eight. A sourdough starter is not one of the options: its yeast population, acidity and bacteria vary from one culture to the next and from one feeding to the next, so there is no general factor to convert it with.

How to use this calculator.

1. 01Choose the yeast you have and the yeast the recipe calls for. If the recipe just says yeast, an American recipe usually means active dry or instant, and a European bakery recipe often means fresh.
2. 02Enter the amount and its unit. Packets and teaspoons are for dry yeast only, and cakes for fresh only; grams and ounces work for all three. Weighing gives the most reliable result, especially for fresh yeast, which cannot be spooned.
3. 03Enter the recipe's flour in cups and say whether it is a sweet dough — more than half a cup of sugar for every 4 cups of flour, as in brioche or cinnamon rolls. These two entries give Red Star's suggested dose.
4. 04If you are replacing fresh yeast with dry, add the extra water shown on top of the recipe's own liquid.
5. 05Before relying on old dry yeast, test it: a little in warm water with a pinch of sugar should foam within about ten minutes. No conversion helps yeast that has died.

The formula.

Everything is first put into grams: a packet is 7 g, a teaspoon of dry yeast 7 ÷ 2.25 = 3.111 g, a cake 2 oz, which is 56.699 g, and an ounce 28.35 g. Each yeast then carries a weight per gram of dry yeast, W: 1 for active dry, 1 for instant and 2.7 for fresh. The converted weight is g_out = g_in × W(to) ÷ W(from), so dry to fresh multiplies by 2.7 and fresh to dry by 1 ÷ 2.7, or 0.3704. When fresh yeast is replaced by either dry yeast, the extra water is 2 × g_out; for every other pair it is zero. A check on that rule: fresh yeast is roughly 70% water, so a 2 oz cake carries about 40 g, close to the 42 g the doubling gives for its 21 g dry replacement. The dose is Red Star's chart: packets = the larger of 1 and 4-cup steps rounded up, ⌈cups ÷ 4⌉, plus one for a sweet dough. Exactly 4 cups takes one packet and 4.1 cups takes two. The dose percentage divides the dose in the target yeast by the flour weight at Red Star's 4 cups to the pound, 113.4 g per cup.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Red Star Yeast (Lesaffre Yeast Corporation). Yeast Conversion Chart, current revision; retrieved 30 July 2026. The primary source for this page's constants and its dose rule. Chart rows: flour 0-4 cups / 1 package / 7 grams / 2 1/4 teaspoons / 2/3 oz fresh cake yeast; 4-8 cups / 2 packages / 14 g / 4 1/2 tsp / 1 1/3 oz; 8-12 cups / 3 packages / 21 g / 6 3/4 tsp / 2 oz (one 2 oz cake); 16-20 cups / 5 packages / 35 g / 11 1/4 tsp / 3 1/3 oz. Also: "One pound of flour is approximately equal to 4 cups of flour"; "If sugar exceeds 1/2 cup per 4 cups flour, add one additional yeast package"; and "Active Dry Yeast or Instant Yeast may be substituted interchangeably when converting from cake yeast".
2. [2]Red Star Yeast (Lesaffre Yeast Corporation). "How to Convert Dry Yeast to Cake Yeast", current revision; retrieved 30 July 2026. Source of the fresh-to-dry weight ratio the whole page is built on: "One 2-oz. cake yeast is equal to three packets (1/4-oz. or 2 1/4 teaspoons each) of dry yeast", and when a 2 oz cake is divided into thirds, "each piece is 0.67 oz (18.9 g)". 18.9 g of fresh per 7 g dry packet gives the factor 2.7.
3. [3]Lesaffre. Saf-instant Red product data page, current revision; retrieved 30 July 2026. Quoted for the manufacturer's own dosing range, "Use 1-3% based on flour weight", which is the figure the page's dose note reports the computed percentage against.
4. [4]King Arthur Baking Company. Ingredient Weight Chart, current revision; retrieved 30 July 2026. Cited for the figures this page records as a conflict rather than uses: instant yeast at "2 teaspoons: 1/5 ounce / 6 grams" and "1 tablespoon: 1/3 ounce / 9 grams", i.e. 3 g per teaspoon against Red Star's 3.11; and all-purpose flour at 120 g per cup against the 113.4 g per cup implied by Red Star's pound-per-four-cups statement. Both differences are named in the output descriptions so a reader comparing the page with King Arthur's numbers can see why they differ.
5. [5]National Institute of Standards and Technology. NIST Special Publication 811, 2008 edition — Guide for the Use of the International System of Units (SI). Table B.8, avoirdupois mass: the ounce is exactly 28.349523125 g and the pound exactly 453.59237 g. Every ounce-to-gram conversion on this page, the 56.69904625 g mass of a 2 oz cake, and the 113.3980925 g-per-cup flour figure derived from Red Star's pound-per-four-cups statement.