FlourScaleThe three common types of baker's yeast
Fresh yeast (also called cake or compressed yeast) is a moist block of live yeast, about 70% water. It is perishable and keeps only a week or two in the fridge. Active dry yeast is yeast dried into larger granules; traditionally it is dissolved in warm water before use. Instant yeast (also sold as rapid-rise, fast-action, quick or bread-machine yeast) has finer granules and can be mixed straight into the flour. Because dried yeast has had its water removed, you need much less of it by weight than fresh yeast.
Conversion factors used
This converter follows King Arthur Baking's professional reference guidelines:
- Fresh yeast × 0.4 = active dry yeast
- Fresh yeast × 0.33 = instant yeast
- Active dry → instant: multiply by about 0.83 (0.33 ÷ 0.4)
These line up with Red Star Yeast's chart, which treats one 7 g (¼ oz) packet of dry yeast as equivalent to about 0.6 oz (17 g) of cake yeast. Teaspoon values assume a 7 g packet holds 2 ¼ teaspoons, about 3.1 g per teaspoon. Manufacturer guidance can differ slightly, and many home bakers simply swap active dry and instant one-for-one, which works fine in most recipes — the instant version will just rise a little faster.
Worked example
A European recipe calls for 21 g of fresh yeast (half a standard 42 g cube).
- Active dry: 21 × 0.4 = 8.4 g (about 2 ¾ tsp)
- Instant: 21 × 0.33 = 6.9 g (about 2 ¼ tsp — one packet)
Going the other way, one 7 g packet of active dry yeast equals 7 ÷ 0.4 = 17.5 g of fresh yeast, or 7 × 0.83 ≈ 5.8 g of instant.
Tips for swapping yeast
- Active dry → instant: mix instant yeast with the dry ingredients; you do not need to dissolve it. Expect rises to be a bit quicker.
- Instant → active dry: if your active dry yeast is old or you want to check it is alive, proof it in some of the recipe's lukewarm water with a pinch of sugar for 5–10 minutes until foamy.
- Fresh yeast: crumble it into the lukewarm liquid. Because it contains water, replacing fresh with dry yeast slightly lowers dough hydration; some bakers add back the difference in water.
- Weigh small amounts. For long, cold ferments that use under 1 g of yeast, a 0.01 g jewellery scale is far more accurate than measuring spoons.
- Sourdough is different. A starter cannot be converted to commercial yeast by a fixed factor; see our starter feeding calculator instead.