Three products sit on the shelf under the same word. Fresh yeast comes as a damp, crumbly block. Active dry yeast comes as coarse granules that traditionally need rehydrating in warm water. Instant yeast comes as fine particles that go straight into the flour. They are the same organism, at very different moisture contents, and a recipe written for one of them will not work if you weigh out the same number of grams of another. This yeast converter does the swap on a convention it names, in the units you actually have in front of you.
Arb Digital builds free tools with sharp boundaries. The live pizza dough calculator works out how much yeast a batch of dough balls needs from scratch, and the sourdough hydration calculator handles a levain rather than commercial yeast. This page does neither: it takes a quantity of yeast you already have or that a recipe already specified, and converts it between the three commercial forms.
What This Yeast Converter Does
It converts a weight, a spoon measure or a packet count of one yeast type into the equivalent of another, and reports the answer in grams, ounces, teaspoons and packets at once. It also expresses the result as a percentage of the flour in your dough, which is how professional formulas are written and the only figure that transfers cleanly between recipes of different sizes.
The reason the conversion is not one-to-one is water. The Chemistry LibreTexts Chemistry of Cooking chapter on yeast gives compressed yeast as roughly 68 to 73 per cent water, active dry at around 7 per cent moisture, and instant dry at around 5 per cent. A gram of fresh yeast is therefore mostly water, and a gram of dry yeast is mostly yeast, which is why a block converts to roughly a third of its weight in granules. The remaining difference between active dry and instant is not water but manufacture: instant yeast is dried more gently into finer particles, so more of the cells survive and it does not need rehydrating.
How to Use It
- Set the two yeast types. Convert from what the recipe specifies to what is in your cupboard, or the other way if you are writing the recipe down.
- Enter the amount and pick its unit. Grams are exact. Teaspoons apply to dry yeasts only, because fresh yeast is crumbled rather than spooned.
- Choose the convention. The default is the manufacturer's published chart. Switch to the other common ratio or enter your own if your recipe came from a source that uses a different one.
- Add the flour weight if you know it. The percentage of flour is the figure worth writing on the recipe card, because it survives being scaled.
- Adjust the timing, not just the quantity. The note under the result says which direction your proof will move.
The Convention This Tool Implements, and the Ones It Does Not
Ratios for yeast conversion are published by several parties and they do not agree. It matters which one a calculator uses, so this one names it.
The default here is the manufacturer's. Red Star's yeast conversion chart and its guide to converting dry yeast to cake yeast both state that one 2 oz cake of fresh yeast equals three quarter-ounce packets of dry yeast, which is 21 g. That gives a fresh-to-dry factor of 21 ÷ 56.7, or about 0.370 — near enough to dividing the fresh weight by 2.7. The same source treats instant yeast as interchangeable one-for-one with active dry by weight, while noting that instant acts faster.
The second option is the ratio that circulates most widely in home baking, usually written as fresh : active dry : instant of 3 : 1.5 : 1. On that convention dry yeast is half the fresh weight and instant is three quarters of the active dry. It gives noticeably more dry yeast than the manufacturer's chart for the same block of fresh, and plenty of good recipes are written against it.
Neither is wrong, and that is the honest answer. Yeast strength varies by strain and by age, the two dry products are not made to a single common standard, and dough behaviour is forgiving enough that both conventions produce bread. Pick the one your recipe was written against, and if you do not know, start with the manufacturer's figure and judge the dough. Custom mode exists so you can lock in whatever your own kitchen has proved works.
The Arithmetic, Worked Through
Two numbers define the whole conversion: d, the grams of active dry yeast equivalent to one gram of fresh, and i, the grams of instant equivalent to one gram of active dry. Every route follows from those. Fresh to active dry multiplies by d; fresh to instant multiplies by d × i; active dry to instant multiplies by i; and each reverse direction divides instead.
Work the anchor. On the manufacturer's convention d is 21 ÷ 56.7 = 0.3704 and i is 1.00. A full 2 oz cake is 56.7 g, and 56.7 × 0.3704 gives 21.0 g of active dry, which is the three packets the chart names. The tool reproduces its own source exactly, which is the check worth having.
Work the default input. Thirty grams of fresh yeast converts to 30 × 0.3704 = 11.11 g of active dry. At 3.1 g per teaspoon that is 3.58 teaspoons, and at 7 g per packet it is 1.59 packets. Against a kilogram of flour it is 1.11 per cent, which sits in the ordinary range for a straight-dough bread.
Spoon and packet figures are conversions of a weight, not measurements in their own right, and they are approximate. A teaspoon of dry yeast is about 3.1 g if it is levelled and a good deal more if it is heaped, and instant granules are finer than active dry so they pack slightly more densely into the same spoon. This is the same reason weight beats volume everywhere else in baking, and it bites harder here because the quantities are small: half a gram of error on a 6 g target is a real proportional change, while half a gram of flour is nothing. Our weight converter and cooking measurement converter cover the wider unit problem.
Conversion Changes the Timing, Not Only the Quantity
This is the point most conversion charts skip, and it causes more disappointment than the ratios do. Swapping yeast types changes the shape of the fermentation as well as its size.
Instant yeast starts faster. Its particles are fine and dry enough to hydrate in the dough itself, so it is active within minutes of mixing and a dough made with it typically reaches the same volume sooner than the same dough made with active dry. If you convert from active dry to instant and keep the recipe's stated proof times, you will very likely over-proof.
Active dry has traditionally been rehydrated first in warm water, and the LibreTexts source above describes rehydration at around 42 to 44 °C for roughly fifteen minutes. If you skip that and throw the granules into the flour, some of the cells never wake up, and the dough is slower than the recipe says rather than faster. Modern active dry is finer than it used to be and many bakers add it dry without trouble, but it remains the type most sensitive to how it is introduced.
Fresh yeast tends to give the slowest, most gradual rise of the three and is prized for the flavour that comes with a longer fermentation. It also has a short life: it needs refrigeration and is spent within a couple of weeks, whereas dry yeast keeps for months and instant keeps for around a year in a sealed pouch.
The practical rule is to convert the weight with this tool and then judge the dough by what it is doing. Proofing time depends on dough temperature far more than on yeast type anyway — a dough at 26 °C ferments roughly twice as fast as the same dough at 18 °C — so a converted recipe is a starting point, and the poke test is the finish.
Reading Yeast as a Percentage of Flour
The single most portable way to record yeast is as a percentage of the flour weight, which is why the fourth grid item exists. A recipe that says "one sachet" tells you nothing until you know how much flour it was for; a recipe that says "1.1 per cent instant yeast" scales to any batch you like.
Typical straight doughs sit in a low single-digit percentage, enriched doughs use more because sugar and fat slow the yeast, and long cold-fermented doughs use much less because they are given many more hours. The tool reports your figure without judging it — the right percentage depends on time, temperature and what you are making. If you want the whole recipe expressed this way, the baker's percentage calculator does it for every ingredient at once.
How This Page Sits Beside Our Other Baking Tools
The boundary in one sentence: this page converts between commercial yeast types, while the pizza dough calculator decides how much yeast a dough needs in the first place and the self-rising flour calculator deals with chemical leavening rather than biological.
For sourdough, the sourdough hydration calculator accounts for the flour and water hidden in a starter, which commercial yeast does not have. For scaling and unit work, use the baker's percentage calculator, the cooking measurement converter and the weight converter.
Arb Digital builds free calculators because genuinely useful pages earn attention and links. If you want tools, calculators or content built for your audience, we can help.
Browse All Free Tools Talk to Arb DigitalCommon Mistakes to Avoid
- Swapping gram for gram between fresh and dry — fresh yeast is around seventy per cent water, so the same weight of dry yeast is roughly three times the dose.
- Keeping the recipe's proof times after converting — instant starts faster and fresh starts slower, so the clock in the recipe no longer describes your dough.
- Measuring yeast in heaped spoons — the quantities are small enough that spoon error is a large proportional error. Weigh it if you can.
- Assuming every published ratio agrees — the manufacturer's chart and the common 3:1.5:1 rule give different answers, and a recipe was written against one of them.
- Using yeast past its life — fresh yeast lasts a couple of weeks refrigerated, and any yeast that has been open and warm for months will under-perform whatever the conversion says.
Related Free Tools From Arb Digital
Size a dough with the pizza dough calculator, express a recipe as percentages with the baker's percentage calculator, and handle a starter with the sourdough hydration calculator. Blend chemical leavening with the self-rising flour calculator, convert units with the cooking measurement converter and weight converter, and browse everything else in the free online tools hub.
Frequently Asked Questions
On the manufacturer's convention used here, one 2 oz cake of fresh yeast — about 56.7 g — equals three 7 g packets of dry yeast, so 21 g. That is a factor of roughly 0.37, or dividing the fresh weight by 2.7.
Because there is no single standard. The manufacturer's chart gives 2 oz fresh to 21 g dry, while the widely circulated home-baking rule of 3 : 1.5 : 1 makes dry yeast half the fresh weight. Yeast strength also varies by strain and age. This tool implements the manufacturer's figure by default and lets you switch.
Not quite. Instant is dried more gently into finer particles with slightly lower moisture, so it can go straight into the flour and acts faster. The manufacturer's convention treats them as interchangeable by weight; other sources use about three quarters as much instant as active dry.
Yes, and that is the part most charts leave out. Instant yeast starts faster than active dry, and fresh yeast usually rises more slowly than either. Convert the weight with this tool, then judge the dough by how it looks and feels rather than by the recipe's stated times.
Traditionally yes, in warm water at around 42 to 44 °C for about fifteen minutes, and skipping it costs you some of the cells. Modern active dry is finer than it once was and many bakers add it dry without problems, but it is the type most sensitive to how it goes in.
A standard sachet is 7 g, which is about 2¼ teaspoons, so a level teaspoon is roughly 3.1 g. Those spoon figures are approximate — granule size and how level the spoon is both shift them — which is why the tool reports grams first.
Not usefully. Fresh yeast is a damp block that is crumbled rather than spooned, so a spoon measure of it is not repeatable. Weigh it, or work in cake sections: a 2 oz cake divides into three pieces of about 17 g.
It depends entirely on the dough and the time available, so this tool reports your figure rather than recommending one. Long cold fermentations use very little, enriched doughs use more because sugar and fat slow the yeast down, and dough temperature affects the outcome more than the percentage does.
This page is a recipe conversion aid, not nutrition or food safety advice. Conversion ratios between yeast types are conventions that published sources disagree on, and yeast activity varies with strain, age, storage and dough temperature, so treat every result as a starting point and judge the dough itself.
