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Yeast conversion calculator

Weigh one kind of commercial yeast and see the other two. Separately, split a starter into the flour and water already in the jar. Those are different jobs. A starter is not a gram of instant yeast.

Quick answer. 5 g of instant yeast is 6.1 g active dry and 15.2 g fresh: 1.67 level teaspoons, or 0.71 of a 7 g packet. A 200 g starter at 100% hydration is 100 g flour and 100 g water.

Commercial yeast
Sourdough starter

Equivalents

Equivalent yeast weights
TypeWeight
Instant yeast5 g
Active dry yeast6.1 g
Fresh yeast15.2 g

Subtract about 0.05 g of dough water if you switch from instant yeast to active dry yeast. Subtract about 10.4 g of dough water if you switch from instant yeast to fresh yeast. Fresh yeast is about 70% water and instant dry yeast about 5% (Lesaffre). Active dry is treated as 5% here too.

In the starter
PartWeight
Flour100 g
Water100 g
Starter total200 g

On 1,000 g of total flour, this jar is 20% inoculation and 10% prefermented flour.

Commercial yeast

The factors are King Arthur Baking’s professional ratios: multiply fresh yeast by 0.33 to get instant, and by 0.40 to get active dry.King Arthur’s yeast referencestates both. Lesaffre describes the same instant ratio as about 1 part instant dry yeast to 3 parts fresh yeast, and notes that fresh yeast is about 70% water while instant dry yeast keeps about 5%.Lesaffre’s comparisonis the source for the water adjustment under the table. Active dry is treated as 5% water here as well.

King Arthur’s home-baking hotline sometimes treats active dry and instant as equal, both fresh × 0.33, because active dry only lags a little and catches up on a long rise.Their fresh-yeast articleuses that simpler home ratio. This calculator uses the professional 0.33 and 0.40 factors. If your long-ferment dough is a bit slow on active dry, time matters more than the 0.07 gap.

Teaspoons and packets

King Arthur’s ingredient weight chart lists 2 teaspoons of instant yeast as 6 g, so a level teaspoon on this chart is 3 g. The same chart lists 2¼ teaspoons as 7 g. A packet is 7 g, which is a little more than 2 level teaspoons. Red Star describes one 7 g packet as about 2¼ teaspoons. Instant and active dry share the spoon weight because King Arthur says they substitute 1:1 by weight or volume. Fresh yeast is in grams only. The two fresh columns use the professional factors, so they are not the same number.

Printable yeast conversion chart
MeasureInstant or active dryFresh, from instantFresh, from active dry
1 level teaspoon3 g9.1 g7.5 g
2 level teaspoons6 g18.2 g15 g
1 packet (7 g)7 g21 g17.5 g

Starter

There is no reliable gram-for-gram swap between a starter and commercial yeast. A jar’s strength depends on when you fed it and how warm it is. What is exact is the split: at 100% hydration the starter is half flour and half water. At 50% hydration it is two parts flour to one part water.

Inoculation on this site is starter weight divided by total flour, not a yeast percentage. Per 100 g of flour, a 100% hydration starter looks like this. The rows are examples of the arithmetic, not a survey of what people bake.

Per 100 g flour, starter at 100% hydration
StarterPrefermented flourWhat that weight is
10%5%10 g of starter per 100 g of flour.
20%10%20 g of starter per 100 g of flour.
30%15%30 g of starter per 100 g of flour.

Put the starter through the baker’s percentage calculator so its water stays inside the hydration. Use the yeast calculator only when the leaven is commercial yeast.

Questions

How do I convert fresh yeast to instant yeast?
Multiply the fresh weight by 0.33. King Arthur’s professional reference uses that factor. The other way, divide the instant weight by 0.33. Active dry uses fresh × 0.40. Five grams of instant yeast is 5 ÷ 0.33 grams of fresh yeast.
How many grams are in a teaspoon of instant yeast?
King Arthur’s ingredient weight chart lists 2 teaspoons of instant yeast as 6 g, so this page uses 3 g per level teaspoon. The same chart lists 2¼ teaspoons as 7 g. Those two lines are not the same spoon weight. Fresh yeast is shown in grams only; this page does not invent a teaspoon weight for fresh yeast.
How much yeast is in a packet?
King Arthur and Red Star both treat a standard packet as 7 g. Red Star says one ¼-ounce (7 g) packet is about 2¼ teaspoons. King Arthur describes a 7 g packet as a slightly heaped 2 teaspoons. Two level teaspoons are 6 g on the chart, so a packet is a little more than 2 level teaspoons. This page uses 7 g per packet and does not force that to equal 7 ÷ 3 teaspoons.
Is active dry yeast the same as instant yeast?
Not in the professional factors used here. The same fresh cake becomes more active dry (× 0.40) than instant (× 0.33). King Arthur’s 2022 article says the two dry yeasts can substitute 1:1 by weight or volume, and the home hotline sometimes treats both as fresh × 0.33. Spoon weights on the chart follow the 1:1 dry substitution. The fresh columns use the professional factors, so they differ.
How do I convert sourdough starter into flour and water?
Flour in the starter is the starter weight divided by (1 + hydration ÷ 100). The rest is water. A 200 g starter at 100% hydration is 100 g flour and 100 g water. There is no reliable conversion from that jar into a gram of commercial yeast.
Do I change the dough water when I change yeast type?
Fresh yeast is about 70% water and instant dry yeast about 5% water, according to Lesaffre. Switching types changes how much water arrives inside the yeast. The calculator shows that adjustment so you do not lose it or count it twice. Next to the dough water it is a small number.

Last reviewed 1 November 2026.

Sources

Spoon weights follow King Arthur’s chart (2 tsp = 6 g). A packet is 7 g. Fresh weights in the chart use the professional 0.33 and 0.40 factors, not a teaspoon of fresh yeast.