Use the same weight. One 7 g packet of active dry yeast becomes 7 g of instant, and the swap holds in both directions. That is what King Arthur and Red Star both tell home bakers, and for one loaf of bread it is the right answer.
It is also only one of four rules currently in print, from three major yeast makers and one named baking authority. Two of the other three fail a test that takes ten seconds: convert one way, convert back, and check whether you land on the number you started with.
The four rules, side by side
Every rule below is quoted from a page that is live today. The columns are what each one tells you to do in each direction, and the last column is what happens when you run it there and back again.
| Source | Instant, in place of active dry | Active dry, in place of instant | Round-trips? |
|---|---|---|---|
| King Arthur, consumer | 1:1 | 1:1 | Yes |
| Red Star | 1:1 | 1:1 | Yes |
| Fleischmann's | equal amount | 25% more | No |
| Peter Reinhart, via Epicurious | 25% less | 25% more | No |
| King Arthur, professional reference | × 0.825 | × 1.212 | Yes |
The last row is not published as an active-dry-to-instant rule at all. It is what falls out of King Arthur's professional fresh-yeast factors, which put active dry at 0.4 times the fresh weight and instant at 0.33. Divide one by the other and you get 0.825 in one direction and 1.212 in the other.
Two of the five entries do not come back to where they started, and both of them are the ones that sound most authoritative — a manufacturer's own instruction sheet, and a baking author whose books are on the shelf of every serious home baker in the country.
The reversal test, run on one packet
Take one 7 g packet of active dry yeast. Convert it to instant using each rule, then convert the answer straight back to active dry using the same source's other instruction.
- Start with active dry
- 7 g (one packet)
- To instant, per the site
- an equal amount, so 7 g
- Back to active dry, per the site
- 25% more, so 8.75 g
- You started with
- 7 g
- The round trip
- gains 1.75 g, a quarter of the packet
Both instructions sit on the same page of the same site, four lines apart. Neither is unreasonable on its own. Together they are not a conversion, because a conversion has to work in both directions.
Reinhart's pair fails the other way. Twenty-five percent less takes 100 g of active dry down to 75 g of instant; twenty-five percent more takes that 75 g back up to 93.75 g. The trip costs you 6.25 percent of the yeast, every time you make it.
Why the 25 percent rule cannot be 25 percent in both directions
The interesting part is that Reinhart states his reason, and the reason gives a different number than the rule does.
“Active dry yeast has about 6 to 7 percent moisture, and about 25 percent of the yeast cells are inactive (dead) due to processing during drying.”
Follow that premise through. If a quarter of the cells in active dry are dead, then any weight of active dry carries three quarters of that weight in live cells, so instant needs to be 0.75 times the active dry weight. That much the rule gets right.
But the reverse is not a subtraction, it is a division. To get the same live cells from active dry you need instant divided by 0.75, which is 1.333 — an increase of 33 percent, not 25. The premise and the rule disagree with each other by eight percentage points.
Bob's Red Mill publishes exactly that non-reciprocal pair — multiply by 1.25 going one way and by 0.75 coming back — on one article, and publishes a flat one-to-one substitution on another. Both articles are live on the same site right now, which tells you how settled this question is not.
What the disagreement is actually worth
Having found four rules that argue with each other, it is worth asking how much daylight is actually between them. Convert that same 7 g packet of active dry into instant under all four, and here is the full spread.
7.00 g
King Arthur and Red Star
one for one, by weight
5.78 g
King Arthur professional
0.825, derived through fresh
5.25 g
Reinhart, 25 percent less
the lowest figure in print
Top to bottom, 1.75 grams. That is a third more yeast at one end than at the other, which sounds decisive until you convert it into the unit a home baker actually works in: just over half a teaspoon, spread across a loaf of bread.
The two rules that do round-trip are also, conveniently, the two closest together. King Arthur's professional factors say you need 1.212 times as much active dry as instant; Fleischmann's says 1.25. Divide one by the other and the professional number and the rule of thumb land within 3.1 percent of each other.
How much yeast is in a packet?
Seven grams, printed on the packet as a quarter of an ounce, and 2¼ level teaspoons. That figure is printed by three independent sources, and the fact that they agree is worth more than any one of them saying it alone.
7 g
One US packet
sold as ¼ oz, which is 7.0 g
2¼ tsp
The same packet in spoons
Red Star, Fleischmann's and King Arthur all print this
3.11 g
One teaspoon of dry yeast
derived: 7 divided by 2¼
Red Star's conversion chart prints one quarter-ounce package as 7 grams and 2¼ teaspoons. Fleischmann's packet-and-jar table gives the same 2¼ teaspoons, and steps it up consistently to 4½ for two packets and 6¾ for three. King Arthur's ingredient weight chart lists 2¼ teaspoons of instant yeast as 7 grams from an entirely separate measurement.
The number to be careful with is the tablespoon. Two and a quarter teaspoons is exactly three quarters of one, so a full tablespoon puts a third more yeast in the dough than the packet holds. The multiples, the jar, and why 7 g is itself a rounded number are all on the packet page.
Three liquid temperatures, not one
Here is the part that matters more than any ratio, and that most pages either skip or get backwards. The three forms of yeast do not want the same liquid temperature, and the difference is large.
- Active dry, dissolved first
- 100–110 °F (38–43 °C)
- Instant, rapid-rise, bread machine
- 120–130 °F (49–54 °C)
- Fresh cake yeast
- 70–90 °F (21–32 °C)
Fleischmann's figures, from its own baking-basics page. The instant band is for the wet ingredients that the dry mix is added to, not for dissolving the yeast on its own.
Read the middle row again. Instant yeast goes into the hottest liquid of the three, twenty degrees above the ceiling for active dry. That is because instant is mixed into the flour first and the flour buffers the heat, while active dry meets the water on its own with nothing to protect it.
Which makes the most repeated warning in home baking — never put yeast in water above 110 °F or you will kill it — a rule that is right for one form and wrong for another. It is good advice for a bowl of water and active dry, and it is not what the manufacturer says to do with instant.
Do you still have to proof active dry yeast?
This is where the sources genuinely part company, rather than merely disagreeing on arithmetic, and any page that reports only one side of it is giving you half the picture.
King Arthur changed its position in 2022. Its consumer article explains that active dry is now made by a gentler drying process that leaves many more live cells, and concludes that dissolving it in warm water first is no longer necessary. Its own professional reference page still describes hydrating active dry before it goes into a dough.
Fleischmann's has not moved at all. Its current instructions tell you to dissolve, and they tell you what to do about the water afterwards.
“Dissolve each packet of Active Dry Yeast in ¼ cup warm water (100–110°F) and proceed with your recipe as it is written. Subtract the water used to dissolve the yeast from the total amount of liquid called for in the recipe.”
That second sentence is the one people forget, and it works in both directions. If you are moving from active dry to instant, the quarter cup that used to dissolve the yeast has to go back into the dough with the rest of the liquid. It was never a separate ingredient; it was part of the hydration, on loan.
Proofing does no harm either way, and it has a second use worth keeping. Dissolving a little yeast in warm water and watching what happens is still the only way to find out whether a jar from the back of the fridge is alive before you commit five hundred grams of flour to it.
The viability test has a pass mark, not a vibe
Most write-ups say to look for bubbles. Both major American manufacturers publish something much stricter than that: a volume the foam has to actually reach, in a measuring cup, within a set time.
- Red Star
- ½ cup water at 110–115 °F, 1 tsp sugar, 2¼ tsp yeast
- Red Star, after 10 minutes
- foam must reach the 1-cup mark
- Fleischmann's
- ¼ cup water at 100–110 °F, 1 tsp sugar, one packet
- Fleischmann's, after 10 minutes
- foam should reach the ½-cup mark
Both tests use a measuring cup as the instrument. Red Star adds that the foam should have a rounded top, and says plainly that yeast which does not reach the mark should be discarded.
A few bubbles will pass a test that has no pass mark. Neither of these does, and that is the point of them. If your yeast produces some foam but never gets near the line, it is alive and weak, which is the state most likely to leave you with a dense loaf and no explanation.
Rapid-rise, quick-rise and bread machine yeast
All of these are instant yeast. Fleischmann's says so about its own range in as many words, and the practical consequence is that you can treat them as one product on the shelf.
“RapidRise Instant Yeast, RapidRise PLUS Instant Yeast and Bread Machine Yeasts are all instant yeasts and can be used interchangeably.”
There is one qualification worth carrying. King Arthur notes that RapidRise is a different strain from the instant yeast Red Star and SAF sell, so "the same category" is not quite "the same organism". For a weeknight loaf that distinction does not surface. For a dough held cold for two days, the yeast that is built to work fast is not necessarily the one you want.
The bread machine is the one place where a real exception is published. King Arthur's guide keeps the one-for-one rule everywhere except a bread machine, where it says to use 25 percent less instant, because a straight swap can push the dough up and then let it collapse inside a sealed tin.
Fresh yeast, and why you probably cannot buy it
Fresh yeast — also sold as cake or compressed yeast — is the form old family recipes are written around, and it is the one swap that changes the method rather than the number. It is also close to unobtainable in most of the United States, which Red Star states about its own product rather than leaving you to discover in a supermarket.
“Fresh cake yeast is only sold in a limited number of stores in the Upper Midwest and Northeastern US. Even in those regions, product availability is 'spotty' and the stores will generally only stock it during the holiday baking season.”
The conversion itself is settled enough. Red Star sells one size, a 2 oz cake, and divides it into three sections each equal to one 7 g dry packet. Fleischmann's says the same thing from the other end: one packet of dry yeast equals one small 0.6-ounce cake, and one 2 oz cake equals three packets.
- Fresh called for
- 17.5 g
- Active dry, at King Arthur's 0.4
- 7.0 g, one packet
- Mass removed from the dough
- 10.5 g
- Most of which was
- water
- Put back
- about 10 g of extra liquid
Fresh yeast is roughly seventy percent water by weight — Lesaffre puts pressed yeast at 30 to 32 percent dry matter. King Arthur's professional reference tells bakers to make up the weight difference between dry and fresh with additional water for exactly this reason.
When the swap genuinely changes the bread
Everything above is about a loaf of bread on a normal schedule, where the forms really are interchangeable. There is a class of dough where they are not, and it is worth knowing which side of the line you are on.
“In the realm of low-moisture doughs with a cold, overnight rise (think bagels, English muffins, or cinnamon rolls), the wrong type of yeast will absolutely impact your bread.”
A wet dough proofed for an hour in a warm kitchen forgives almost anything. A stiff dough held cold overnight does not, because there is less water to rehydrate the yeast and far more time for a difference in vigour to compound into a difference you can see.
Sugar is the other threshold. Red Star's own chart says that once a recipe passes half a cup of sugar to four cups of flour, it needs an extra package of yeast, because sugar in quantity slows fermentation down. Lesaffre sells a separate osmotolerant yeast, SAF Gold, and describes it as developed for doughs at five percent sugar on flour weight or more.
How much yeast for the flour you have
Red Star publishes its recommendation against flour rather than against a recipe, which is the more useful way round when you are scaling something.
- 0 to 4 cups flour
- 1 packet — 7 g, 2¼ tsp
- 4 to 8 cups
- 2 packets — 14 g, 4½ tsp
- 8 to 12 cups
- 3 packets — 21 g, 6¾ tsp
- 12 to 16 cups
- 4 packets — 28 g, 9 tsp
- 16 to 20 cups
- 5 packets — 35 g, 11¼ tsp
Red Star's conversion chart. Read against King Arthur's 120 g cup of all-purpose flour, one packet across four cups works out at about 1.5 percent of the flour weight — which puts a 500 g loaf at almost exactly one packet.
One caution on that chart. The sugar note lower down the same page calls the extra package "2 teaspoons", where the chart itself calls a package 2¼. It is an eleven percent difference on a rounding, and it is a good illustration of why weight is the figure to trust and the spoon is the figure to approximate.
Storage, and how long yeast really lasts
Both manufacturers land on the same headline number for an opened container, and both are more specific than the internet's usual advice.
Do
- Write the date on the jar the day you open it
- Keep opened dry yeast in the fridge or freezer and use it within four months
- Take out only what you need and let it come to room temperature first
- Keep fresh cake yeast refrigerated and use it well inside its date
- Weigh yeast rather than spooning it, whenever a scale is to hand
Don't
- Assume a rule that reads 25 percent in both directions is a conversion
- Put instant yeast on a 110 °F ceiling meant for dissolving active dry
- Forget to return the proofing water to the dough when you switch to instant
- Swap yeast weight for weight with sourdough starter, which is mostly flour and water
- Add extra yeast to hurry a dough, since flavour is what fermentation time buys
Red Star says opened jars go in the refrigerator or freezer, prefers the freezer, and puts the working life at four months. Fleischmann's says four months in the fridge. Red Star adds a detail worth having: dry yeast never freezes solid, so it goes straight from the freezer into a recipe once it has warmed for twenty minutes or so.
The short version
If a recipe calls for one and you have the other, use the same weight and start watching the dough. Active dry starts more slowly, which is worth roughly fifteen to twenty minutes on an hour-long rise, and the manufacturer that sells it says the same thing in its own words.
“Active dry yeast has a slower rate of action than instant yeast; therefore, your dough MAY take slightly longer to rise. Simply monitor your dough while it is rising and adjust the time as needed.”
That is the answer the four competing rules were circling all along. The weight is a starting point, not a finish line, and no ratio in print can tell you what a particular jar of yeast will do in a particular kitchen on a particular day. The dough can.
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