Audited —·Last updated 31 Jul 2026·5 citations·Tier 2·0 uses

Yeast Converter

Convert active dry, instant and fresh cake yeast by weight on Red Star's published chart, with the packet dose for your flour and Lesaffre's water rule.

Yeast Converter

Yeast you have
Yeast the recipe wants
How much of the yeast you have, in the unit chosen below.
Measured in
Used for the second answer on the page: how much yeast Red Star's chart recommends for this much flour, independent of your conversion. Their chart is one packet per four cups, and they note that one pound of flour is approximately four cups.
cups
More than 1/2 cup sugar per 4 cups flour?
Yeast to use
56.7
The equivalent weight of the target yeast. Everything on this page converts by weight, because that is how both Red Star and Lesaffre publish their figures — a spoon of instant yeast and a crumbled lump of fresh yeast are not comparable volumes.
Yeast to use (ounces)
2 oz
In teaspoons
0 tsp
In packets
0
In 2 oz cakes
1
You have (grams)
21 g
Conversion factor
2.7
Extra water to add
0 g
Red Star's dose for this flour
3
That dose in your target yeast
56.7 g
Dose as % of flour weight
4.17
Dose note
Red Star's chart puts 3 packets — 21 g of dry yeast — on 12 cups of flour, which is 56.7 g of fresh (compressed) yeast, or 4.17% of the 1,360.78 g of flour. Lesaffre specifies instant yeast at 1-3% of flour weight; fresh yeast is about 2.7 times that by weight.
Summary
21 g of active dry yeast converts to 56.7 g of fresh (compressed) yeast — 1 cake of 2 oz.

Background.

Three yeasts sit on supermarket and bakery shelves — active dry, instant, and fresh compressed yeast sold as a cake — and recipes name them interchangeably without telling you the exchange rate. This converter uses the figures Red Star publishes for its own products. One packet of dry yeast is a quarter ounce, 7 grams, or 2 1/4 teaspoons. One 2-ounce cake of fresh yeast equals three of those packets, and Red Star spells out the weight when you divide a cake into thirds: "each piece is 0.67 oz (18.9 g)". That gives the whole page its anchor — 18.9 grams of fresh yeast per 7 grams of dry, a factor of 2.7 by weight.

Active dry and instant swap one for one. Red Star states that "Active Dry Yeast or Instant Yeast may be substituted interchangeably", and King Arthur, independently, says to "substitute instant yeast 1:1 by weight or volume for any active dry yeast called for in your recipe". That matters because a widely repeated kitchen rule says to use twenty-five percent less instant than active dry, and no authority consulted for this page supports it as a general substitution. The calculator uses 1.0, and its test suite asserts the factor is 1.0 and explicitly not 0.75, so the folk figure cannot creep in later.

Going the other way — replacing fresh yeast with a dry one — has a step most conversion charts leave out. Fresh yeast is mostly water, and taking it out of a formula takes that water with it. Lesaffre's technical data sheet for SAF-Instant instructs that extra water be added at approximately double the weight of the dry yeast used, and their own table checks it: a pound of compressed yeast becomes 5.5 ounces of instant plus 11 ounces of water, and 11 is exactly twice 5.5. The calculator reports that water figure whenever the conversion runs from fresh to dry, and zero otherwise. The same data sheet says instant "will replace compressed yeast on an average at 33-40 percent of compressed yeast levels"; this page's 1-in-2.7 works out at 37.0 percent, comfortably inside that band, which is the cross-check that Red Star's packet arithmetic and Lesaffre's industrial figure describe the same thing.

The page answers a second question alongside the conversion: how much yeast this much flour actually wants. Red Star's chart is one packet per four cups of flour, stepping up a packet at each four-cup boundary, with one additional packet when the sugar exceeds half a cup per four cups because sugar competes with the yeast for water and slows fermentation. The calculator reproduces those rows exactly, including the fact that they are half-open at the top — four cups takes one packet, four and a bit takes two — and expresses the dose in your target yeast and as a percentage of the flour weight, which is how Lesaffre specifies its own product at 1 to 3 percent of flour weight.

One thing the page deliberately will not do is convert a sourdough starter. There is no manufacturer figure and no standards-body figure for a starter-to-commercial-yeast equivalence, and there cannot be a general one: a starter's viable cell count, its acidity and its ratio of yeasts to lactic-acid bacteria differ between cultures and between successive feedings of the same culture. Rather than invent a number that would look authoritative and be wrong, starter is simply absent from both dropdowns, and the Sourdough Calculator is linked instead. Two smaller limits belong here too. Fresh yeast is perishable and is not stocked everywhere, so the dry-to-fresh direction is often academic outside a bakery supply. And no conversion figure can rescue dead yeast — proof half a teaspoon in warm water and watch for a vigorous fizz before you trust any arithmetic on this page.

What is yeast converter?

Baking yeast is a single organism, Saccharomyces cerevisiae, sold in three forms that differ in moisture content and therefore in how much of the packet is actually yeast. Fresh or compressed yeast — the cake — is about 70 percent water and has to be refrigerated and used within days. Active dry yeast is granulated and dried to a few percent moisture, with a proportion of dead cells forming a protective coat, which is why older recipes tell you to dissolve it in warm water first. Instant yeast is dried differently, in finer particles that hydrate on contact, so it can be mixed straight into dry ingredients.

Because the water fraction differs, equal leavening power means unequal weights. Red Star's published figures make the exchange concrete: 7 g of dry yeast per 18.9 g of fresh, and active dry interchangeable with instant. That is the whole conversion, and it is a weight ratio rather than a volume ratio because the three forms have entirely different bulk densities.

The range of validity is ordinary bread and sweet-dough baking with commercial yeast. It is exact arithmetic on published constants, so there is no error term — but the constants themselves are manufacturer figures rounded to the tenth of a gram, and Red Star's own 18.9 g for two-thirds of an ounce is a rounding up from 18.8997 g, which is why a converted 2 oz cake comes back as 2.99995 packets rather than exactly 3.

What the arithmetic cannot cover: sourdough starter, brewing and wine yeasts, nutritional yeast, dead or expired yeast, and fermentation timing. A conversion tells you how much to use, not how long to wait.

How to use this calculator.

  1. Pick the yeast you have and the yeast the recipe wants. If either is a sourdough starter, stop — this page cannot convert a starter and says why. Use the Sourdough Calculator instead.
  2. Enter the amount and choose its unit. Packets and teaspoons are dry-yeast measures; cakes is a fresh-yeast measure; grams and ounces work for anything. The calculator refuses a mismatch rather than quietly applying the wrong density to it.
  3. Read the headline weight. That is the amount of the target yeast to use, and the packet, teaspoon or cake count beside it is the same figure in kitchen units.
  4. If you are replacing fresh yeast with a dry one, look at the extra-water figure. Lesaffre's rule is to add about double the weight of the dry yeast in water, because the fresh yeast you removed was mostly water. Skipping it leaves the dough noticeably stiffer than the recipe intended.
  5. Enter the recipe's flour in cups to get the second answer: how much yeast Red Star's chart puts on that much flour, independent of your conversion. It is a useful sanity check when a recipe's yeast quantity looks odd.
  6. Set the sugar question to yes for a sweet dough — brioche, cinnamon rolls, panettone. Red Star's chart adds a whole extra packet above half a cup of sugar per four cups of flour, because sugar competes with the yeast for water.
  7. Proof the yeast before you commit. Half a teaspoon in a little warm water should foam vigorously within a few minutes. No number on this page can detect a jar that has gone flat, and that is the most common reason a conversion appears to fail.

The formula.

g_out = g_in × W(to) ⁄ W(from) ; water = 2 × g_out (fresh → dry only)
g_in · your yeast, normalised to gramsW(activeDry) = 1 · grams per gram of dry yeastW(instant) = 1 · Red Star and King Arthur both say 1:1W(fresh) = 2.7 · Red Star: 18.9 g fresh per 7 g dry packetpacket · 1⁄4 oz = 7 g = 2 1⁄4 tsp (Red Star)cake · 2 oz = 56.699 g (Red Star, NIST ounce)dose · 1 packet per 4 cups flour, +1 if sugar > 1⁄2 cup per 4 cups

The conversion is one multiplication once every quantity is expressed in grams. Each yeast type carries a weight-per-dry-gram figure: active dry 1, instant 1, fresh 2.7. The factor is the target's figure divided by the source's, and the answer is your weight times that factor.

Where the constants come from. Red Star's packet is defined as a quarter ounce, 7 g, or 2 1/4 teaspoons; that single sentence gives both the packet mass and the teaspoon density of 7 / 2.25 = 3.1111 g per teaspoon. Their article on converting dry yeast to cake yeast states that one 2 oz cake equals three packets and that each third of a cake is 0.67 oz, 18.9 g. So 18.9 g of fresh yeast does the work of 7 g of dry, and 18.9 / 7 = 2.7. The 1:1 between active dry and instant is Red Star's "may be substituted interchangeably", confirmed independently by King Arthur's "substitute instant yeast 1:1 by weight or volume". Every ounce-to-gram conversion uses NIST's exact avoirdupois ounce, 28.349523125 g, so a 2 oz cake is 56.69904625 g.

Unit outputs that do not apply read zero rather than a misleading number. Teaspoons and packets read 0 for a fresh-yeast target because fresh yeast is crumbled rather than spooned and is not sold in quarter-ounce packets; cakes reads 0 for a dry target. This is the same convention the site's cooking converter uses for its canonical-unit fields, and it is preferable to reporting a teaspoon figure computed from the wrong density.

The water rule. Lesaffre's SAF-Instant technical data sheet instructs that when instant yeast replaces compressed yeast, extra water be added at approximately double the weight of the yeast, and their table confirms it: 1 lb compressed becomes 5.5 oz instant plus 11 oz water. The calculator applies the doubling to the converted dry weight, and only in the fresh-to-dry direction; every other pairing returns zero. Their stated replacement band, 33 to 40 percent of compressed yeast levels, is the cross-check on the 2.7 factor: 1 / 2.7 = 37.037 percent, inside the band.

The dose. Red Star's chart puts one packet on up to four cups of flour, two on four to eight, three on eight to twelve, and so on, and adds one extra packet when the sugar exceeds half a cup per four cups. That is a ceiling function on the flour divided by four, with a floor of one packet, and the ceiling is taken on the unrounded value so the rows stay half-open at the top: exactly four cups takes one packet, four and a millionth takes two. The flour weight behind the percentage uses Red Star's own basis that a pound of flour is approximately four cups, so 113.3980925 g per cup.

Rounding stage. Nothing is rounded at an intermediate step. Every quantity is carried in arbitrary-precision decimal arithmetic and rounded exactly once, at the point the result leaves the calculator, to ten decimal places. The only visible consequence of the sources' own rounding is that a true 2 oz cake converts to 2.99995 packets rather than exactly 3, because Red Star rounded two-thirds of an ounce — 18.899682 g — up to 18.9 g.

Classification stage. This page classifies nothing. Every output is a mass, a count or a ratio, and the two text outputs state computed figures beside a published range without attaching a verdict word to either, so there is no band edge anywhere that could be decided from a rounded value. The one step boundary on the page is the integer packet count, and it is tested immediately below, at, and immediately above each of Red Star's four-cup row edges.

A worked example.

Example

A baker has three packets of active dry yeast and a European recipe written for fresh compressed yeast, with twelve cups of flour in the formula. Three packets at Red Star's quarter-ounce packet make fromGrams 3 x 7 = 21 g, which is the figure Red Star's own chart prints for the eight-to-twelve-cup row. The conversionFactor from dry to fresh is 2.7, taken from their statement that each third of a 2 oz cake weighs 0.67 oz or 18.9 g and equals one 7 g packet: 18.9 divided by 7 is 2.7. So convertedGrams is 21 x 2.7 = 56.7 g of fresh yeast. In ounces that is convertedOunces = 56.7 / 28.349523125 = 2.0000336425 oz, and in cakes convertedCakes = 56.7 / 56.69904625 = 1.0000168213 — one 2 oz cake, exactly as Red Star's chart prints for this row. The tiny excess over 2 is the source's own rounding: two-thirds of an ounce is 18.899682 g and Red Star rounds it to 18.9. Because the target is fresh yeast, convertedTeaspoons and convertedPackets both read 0 rather than a number computed from the wrong density — fresh yeast is crumbled, not spooned, and is not sold in packets. extraWaterGrams reads 0 too, because Lesaffre's doubling rule applies to the fresh-to-dry direction, not this one. The second answer comes from the flour. Twelve cups divided by four is three, so recommendedPackets is 3, matching the chart row reached independently of the conversion, and recommendedGrams is 3 x 7 x 2.7 = 56.7 g of fresh yeast. At Red Star's basis of a pound of flour to four cups, twelve cups weigh 1,360.78 g, so dosePercentOfFlour is 100 x 56.7 / 1360.78 = 4.1667367553 percent — about 2.7 times Lesaffre's 1 to 3 percent instant-yeast figure, which is exactly what the weight ratio between the two yeasts predicts.

amount3
to Typefresh
from TypeactiveDry
amount Unitpackets
sugar Richno
flour Cups12

Frequently asked questions.

Do I really use the same weight of instant yeast as active dry?
Yes, on the evidence of both authorities consulted. Red Star's conversion chart states that "Active Dry Yeast or Instant Yeast may be substituted interchangeably", and King Arthur's article on the two says to "substitute instant yeast 1:1 by weight or volume for any active dry yeast called for in your recipe", with no percentage reduction mentioned. A widely repeated kitchen rule says to use twenty-five percent less instant, and it is not supported by either source as a general substitution — King Arthur's own qualification concerns bread machines specifically, where the higher rise temperature can cause over-rising. This calculator uses 1.0 and its test suite pins that value against 0.75 and 1.25 so the folk figure cannot slip in. What does change is method: instant yeast can go straight into the dry ingredients, while active dry was traditionally dissolved in warm liquid first.
Why does replacing fresh yeast need extra water?
Because fresh yeast is roughly seventy percent water, and taking it out of the formula takes that water with it. Lesaffre's technical data sheet for SAF-Instant is explicit: when instant yeast replaces compressed yeast, extra water is required, approximately double the weight of the yeast. Their own conversion table satisfies the rule exactly — one pound of compressed yeast becomes 5.5 ounces of instant plus 11 ounces of added water, and 11 is twice 5.5. The calculator reports that figure whenever the conversion runs from fresh to a dry yeast and zero in every other direction. Skip it and the dough will be measurably stiffer than the recipe intended, which at bakery scale is the difference between a workable dough and one that fights the mixer. At home, on a single loaf, the missing water is a few grams and rarely decisive.
Why can't this convert my sourdough starter?
Because there is no figure to convert with. No yeast manufacturer and no standards body publishes a starter-to-commercial-yeast equivalence, and the reason is not neglect: a starter's viable cell count, its acidity, and its ratio of wild yeasts to lactic-acid bacteria differ between cultures, between kitchens, and between successive feedings of the same jar. A number that averaged across all of that would be confidently wrong for almost every specific starter, which is worse than no number at all — the same reasoning that keeps unsourced score tables and dosing figures off this site. Starter is therefore absent from both dropdowns rather than present with a caveat. What you can do instead is resolve the whole formula in starter terms: the Sourdough Calculator takes a levain percentage and a starter hydration and works out the flour, water and salt around it.
How much yeast should a recipe use per cup of flour?
Red Star's chart is one packet — 7 g, 2 1/4 teaspoons — for up to four cups of flour, and it steps up a packet at each four-cup boundary. That works out at about 1.5 percent of the flour weight on their own basis that a pound of flour is roughly four cups. Lesaffre specifies its Saf-instant Red at 1 to 3 percent of flour weight, so the chart's dose sits comfortably in the middle of the manufacturer's own range. The chart carries one important exception, which the calculator implements: "If sugar exceeds 1/2 cup per 4 cups flour, add one additional yeast package." Sugar draws water away from the yeast osmotically and slows fermentation, so sweet doughs need more. Note that the chart is a maximum-rise-speed recommendation, not a rule — many artisan formulas use a fraction of a percent of yeast and a long cold fermentation for flavour.
Why does a 2 oz cake convert to 2.99995 packets instead of 3?
Because Red Star rounded, and the calculator does not hide it. They state that a 2 oz cake divides into three pieces of 0.67 oz, and give the weight of a piece as 18.9 g. But two-thirds of an avoirdupois ounce is 18.899682 g, not 18.9 — a rounding up of about three ten-thousandths of a gram. Building the page's 2.7 factor from the published 18.9 g and then converting a true 2 oz cake (56.69904625 g at NIST's exact ounce) therefore returns 20.99965 g of dry yeast, which is 2.99995 packets. Red Star's own printed answer for that row is 3 packets, and it is right for any practical purpose. The calculator shows the unrounded arithmetic rather than snapping to the round number, so that if you scale to a bakery batch the discrepancy remains visible and traceable instead of accumulating silently.
Can I measure yeast by the spoon instead of weighing it?
You can for dry yeast, and the page gives you the teaspoon figure — but the two authorities disagree slightly on the density and it is worth knowing by how much. Red Star's packet statement gives 7 g per 2 1/4 teaspoons, so 3.111 g per teaspoon. King Arthur's ingredient chart gives instant yeast at 6 g per 2 teaspoons and 9 g per tablespoon, so 3.0 g per teaspoon. The calculator uses Red Star's figure because the packet is the unit everything else on the page is anchored to; on their density 21 g reads as 6.75 teaspoons, and on King Arthur's it would read as 7.0. That is a quarter of a teaspoon on a three-packet quantity, well inside the tolerance of a bread dough. For fresh yeast there is no spoon figure at all, which is why that field reads zero: a crumbled lump has no reproducible volume.
Is fresh yeast better than dry?
It is different, and the difference is smaller than tradition suggests. Fresh compressed yeast has a reputation among professional bakers for a slightly cleaner, less yeasty flavour and a fast, vigorous start, and it remains standard in some European bakeries. Against that, it is about seventy percent water, so it is perishable — days in a refrigerator, not months in a cupboard — and it is simply not stocked in most retail groceries outside bakery-supply channels, which makes the dry-to-fresh direction of this converter academic for many home bakers. Red Star's own position is that any of the dry yeasts may be substituted when converting from cake yeast, which is the pragmatic answer. If you have fresh yeast and a recipe wants dry, convert it and use it; if you have dry yeast and a recipe wants fresh, convert it, add nothing, and expect a very similar loaf.

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". Independence: primary. Access: open.
  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. Independence: primary. Access: open.
  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. Independence: primary. Access: open.
  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. Independence: primary. Access: open.
  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. Independence: primary. Access: open.
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