Yeast Type Conversion Calculator

The Mathematics of Yeast Equivalence

Commercial yeast products differ mainly in their moisture content and how densely yeast cells are packed. Active dry granules are partially dehydrated, instant granules are dry but more porous and fast-acting, and fresh cake yeast is mostly water. To substitute one type for another, you scale the weight according to relative potency.

Key Variables

• m_a = mass of active dry yeast (grams)
• m_i = mass of instant yeast (grams)
• m_f = mass of fresh cake yeast (grams)

Core Formulas

The basic relationships can be written as proportional formulas. In plain-text form:

• Instant from active dry: m_i = 0.75 × m_a
• Fresh cake from active dry: m_f = 2.5 × m_a

The same relationships can be expressed in MathML for clarity:

To convert in the opposite direction you divide instead of multiply:

• Active dry from instant: m_a = m_i ÷ 0.75
• Active dry from fresh cake: m_a = m_f ÷ 2.5

Sample Conversion Table

The table below shows typical equivalents. All values are approximate, based on the factors above.

Interpreting Your Conversion Results

The calculator outputs the equivalent yeast weights in grams. Use these numbers as starting points, not rigid rules. In practice, dough behavior is influenced by dough temperature, flour strength, hydration, sugar and fat content, and how active your yeast is.

What the Numbers Mean for Your Dough

• If the converted amount seems very small (for example, under 1 g), treat it as approximate and measure with a precise scale or use volume measures (teaspoons) with care.
• If you use slightly more yeast than the calculator suggests, your dough will likely rise faster and may develop more yeasty or alcoholic flavors.
• If you use slightly less yeast, the dough will rise more slowly but can develop more complex flavor if you allow enough time.

The goal of conversion is to keep proofing time in the same range as the original recipe. After converting, watch the dough itself: bake when it has actually risen enough, even if the clock says otherwise.

Worked Example: Swapping Active Dry for Instant Yeast

This example shows how you might use the calculator alongside the formulas above.

Example 1: Recipe Calls for Active Dry, You Have Instant

Scenario: Your recipe specifies 7 g of active dry yeast, but you only have instant yeast.

1. Enter 7 into the amount field.
2. Select Active Dry as the source yeast type.
3. Run the conversion to see the equivalent amount of instant yeast.

Using the formula m_i = 0.75 × m_a:

• m_i = 0.75 × 7 g = 5.25 g instant yeast

You would round to a convenient value, for example 5.3 g, depending on your scale.

Example 2: Recipe Calls for Instant, You Have Fresh Cake

Scenario: A European-style bread formula specifies 3 g of instant yeast, but your bakery stocks only fresh cake yeast.

1. Enter 3 into the amount field.
2. Select Instant as the source type.
3. Use the calculator to convert to active dry, then to fresh cake, or directly if supported by the interface.

Conceptually, you can go via active dry:

• m_a = m_i ÷ 0.75 ≈ 3 ÷ 0.75 = 4 g active dry equivalent
• m_f = 2.5 × m_a = 2.5 × 4 = 10 g fresh cake

You would use approximately 10 g of fresh cake yeast instead of 3 g instant.

Comparing Active Dry, Instant, and Fresh Cake Yeast

Although these yeast types can be substituted by weight, they are not identical in how they behave in dough. The table below summarizes practical differences that matter for baking.

Assumptions and Limitations of This Calculator

The conversion factors used here are practical approximations for everyday baking, not precise scientific measurements. Keep these assumptions and limitations in mind:

• Standard commercial yeast only: The tool assumes typical supermarket or professional bakery brands of baker’s yeast. It does not apply to nutritional yeast, brewer’s yeast, wine yeast, or sourdough starter.
• Average potency: The 0.75 and 2.5 factors reflect average strengths across many products. Actual activity varies by brand, manufacturing process, and batch.
• Freshness and storage: Yeast that is old or stored poorly (for example, too warm or not sealed) will be less active than new yeast. The calculator cannot account for this.
• Recipe style differences: High-sugar, high-fat, very cold, or very stiff doughs put extra stress on yeast. Some recipes compensate by increasing yeast compared with lean, room-temperature doughs.
• Rounding and measurement error: Kitchen scales often round to 0.1 g or 1 g. Very small quantities may not be perfectly accurate, and rounding is normal.
• Rise time still matters: The results are guidelines. Always judge fermentation by dough volume and feel, not just by the clock or by the converted number.

Because of these factors, the calculator is best viewed as a smart starting point. Adjust proofing times, and if necessary yeast amounts, based on how your dough performs.

Practical Tips for Substituting Yeast Types

Beyond simple weight conversion, a few handling adjustments can improve your results when swapping yeast types.

When Replacing Active Dry with Instant

• Use about 25% less instant yeast by weight than active dry.
• You can usually skip proofing and mix instant yeast directly into the flour.
• Keep dough temperature and hydration similar to the original recipe to maintain proofing times.

When Replacing Instant with Active Dry

• Use about 33% more active dry by weight than instant.
• Consider proofing active dry in warm water first to confirm it is alive, especially if the yeast is older.
• Be prepared for slightly longer or shorter rise times depending on your kitchen temperature.

When Using Fresh Cake Yeast

• Convert from active dry using the factor of 2.5× by weight.
• Store fresh yeast in the refrigerator and use it before the expiration date for best activity.
• Crumble or dissolve fresh yeast in a portion of the recipe liquid before adding to flour.

Frequently Asked Questions

How many grams are in a standard packet of yeast?

In many regions, a typical packet of active dry or instant yeast contains about 7 g. Always check the label on your specific brand, as some markets use slightly different packet sizes.

Can I swap instant yeast for active dry 1:1 by weight?

You can often substitute 1:1 in casual home baking and simply watch the dough, but to match the original recipe more closely, use about 25% less instant yeast than active dry. The calculator applies this more precise ratio.

Do I need to proof instant yeast?

Most instant yeast can be mixed directly with the flour and does not require proofing. Some bakers still proof it to check viability, but this is optional unless your yeast may be old or has been stored poorly.

Does this calculator work for sourdough starter?

No. Sourdough starter is a mixture of wild yeast, bacteria, flour, and water, with highly variable strength. There is no simple, universal gram-for-gram conversion between starter and commercial yeast. Follow a recipe designed specifically for sourdough if you want to use a starter.

Will I need to change rise times after converting yeast types?

Possibly. The calculator aims to keep yeast strength similar, but actual rise time still depends on temperature, dough composition, and yeast freshness. Use the converted amount as a guide, then rely on dough volume and texture to decide when to move to the next step.