The conversion ratios
Yeast types differ in how many active cells they contain per gram. The widely used substitution ratios are:
instant : active dry : fresh = 1 : 1.25 : 3 by weight
- Fresh → instant: divide by 3 (some bakers use 2.5).
- Instant → active dry: multiply by 1.25. Many yeast brands say the two can be swapped 1:1 in most recipes; the 25% extra simply makes up for slightly lower activity.
Grams, teaspoons and packets
A standard US packet holds ¼ oz (7 g), about 2¼ teaspoons, so a teaspoon of dry yeast weighs roughly 3.1 g. Measuring by weight is more accurate, especially for small amounts.
Using active dry yeast
Active dry yeast traditionally gets dissolved in some of the recipe's lukewarm water first. Instant yeast can be mixed straight into the flour. Fresh yeast is crumbled in or dissolved in water and keeps for only a couple of weeks in the fridge.
Frequently asked questions
How much instant yeast replaces fresh yeast?
Use one third of the weight: 21 g of fresh yeast becomes 7 g of instant yeast.
Can I use active dry yeast instead of instant?
Yes. Use about 25% more by weight (or the same amount and allow a little more rising time) and dissolve it in some of the water first.
How many grams is a packet of yeast?
A standard US packet is ¼ oz, or 7 g, about 2¼ teaspoons.