Yeast Converter: Fresh, Dry & Sourdough Starter

Convert between fresh yeast, dry yeast, and sourdough starter with precision. Get recipe adjustments when using sourdough starter to maintain perfect hydration.

1. Select Yeast Type

2. Enter amount

Conversions

Enter amount

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Frequently Asked Questions

What is the difference between fresh and dry yeast?

Fresh yeast contains about 70% water, while dry yeast contains about 8%. The conversion factor is 1 part dry equals 3 parts fresh yeast. Dry yeast is more potent and shelf-stable, making it ideal for long-term storage.

How much sourdough starter do I need?

Sourdough starter is 100% hydration by default (equal parts flour and water). To replace 1g fresh yeast, you need 5g starter (1:5 ratio). Always adjust your recipe to account for the extra flour and water in the starter.

Why do I need to adjust my recipe for sourdough?

Sourdough starter contains both yeast and flour/water. When you add it, you're adding ingredients to your recipe. You must subtract the equivalent flour and water from your total to maintain correct hydration and structure.

Can I use instant yeast instead of active dry yeast?

Instant yeast is a type of active dry yeast that is finely milled. The conversion ratio remains the same: 1:3 between dry and fresh. Instant yeast may require slightly less liquid due to its fine particle size.

# Yeast Conversion Formula & Science Guide

Yeast conversion is essential for baking consistency. Whether you're replacing commercial yeast with sourdough starter or adjusting between fresh and dry varieties, understanding the exact ratios ensures reliable fermentation and consistent results.
1:3 Dry to Fresh Ratio
1:5 Fresh to Sourdough
70% Water in Fresh Yeast
8% Water in Dry Yeast

# Types of Leavening Agents & Their Properties

Fresh Yeast (Cake Yeast)

Living yeast cells suspended in starch and moisture.

  • Potency: 100% (baseline)
  • Shelf life: 2-3 weeks refrigerated
  • Water content: ~70%
  • Best for: Professional bakers, immediate use

Dry Yeast (Instant)

Desiccated yeast cells, more concentrated than fresh.

  • Potency: 3x fresh yeast
  • Shelf life: 1-2 years unopened
  • Water content: ~8%
  • Best for: Home bakers, long-term storage

Sourdough Starter

Wild yeast and bacteria culture at 100% hydration.

  • Potency: 1 part = 5 parts fresh yeast
  • Shelf life: Indefinite with care
  • Water content: 50% (equal parts flour)
  • Best for: Complex flavor, slow fermentation

# Conversion Ratios & Mathematical Formula

Source Yeast Target Yeast Conversion Formula Example
Fresh YeastDry YeastFresh ÷ 3 = Dry30g Fresh = 10g Dry
Dry YeastFresh YeastDry × 3 = Fresh10g Dry = 30g Fresh
Fresh YeastSourdough (100%)Fresh × 5 = Sourdough20g Fresh = 100g Starter
Sourdough (100%)Fresh YeastSourdough ÷ 5 = Fresh100g Starter = 20g Fresh
Dry YeastSourdough (100%)Dry × 15 = Sourdough10g Dry = 150g Starter
Sourdough (100%)Dry YeastSourdough ÷ 15 = Dry150g Starter = 10g Dry

Critical: Recipe Adjustment for Sourdough

Warning
When substituting fresh or dry yeast with sourdough starter, you MUST adjust your recipe. Sourdough starter contains 50% flour and 50% water. If your conversion requires 100g starter, subtract 50g flour and 50ml water from your recipe to maintain correct hydration.

# Fermentation Characteristics by Yeast Type

Yeast Type Fermentation Speed Flavor Development CO₂ Production
Fresh YeastFast (2-3 hrs)Neutral to mildHigh and rapid
Dry YeastMedium (3-4 hrs)Slightly more complexConsistent
SourdoughSlow (8-48 hrs)Complex, tangyGradual, sustained
Pro Tip: Temperature Adjustments
Cold fermentation with sourdough (2-4°C for 8-16 hours) develops superior flavor and structure compared to warm fermentation. This is why professional bakeries prefer sourdough for long-fermented breads.
Our converter simplifies the math so you can focus on perfecting your baking technique and flavor development.

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