Yeast Calculator
The Yeast Calculator determines optimal yeast amounts and calculates starter requirements for liquid yeast.
How to Use
Direct Pitch
Enter Batch Volume - Post-boil volume into fermenter
Enter Original Gravity - Target OG
Select Yeast Type - Liquid or dry
Enter Package Info - Manufacture date and count
View Requirements - Packages needed
Yeast Starter
Enter Batch Info - Volume and gravity
Select Starter Method - Stir plate or shaking
Enter Starter Volume - Typically 1-2L
View Results - Final cell count
Pitch Rates
Recommended Pitch Rates
By Beer Type
Ales: 0.75 million cells/ml/°P (standard)
Lagers: 1.5 million cells/ml/°P (double ale rate)
High Gravity (>1.065): 1.0-1.25 million cells/ml/°P
Belgian/Wheat: 0.5-0.75 million cells/ml/°P
Factors Affecting Pitch Rate
Wort Gravity: Higher gravity needs more yeast
Beer Style: Lagers need more than ales
Yeast Health: Older yeast needs higher pitch rate
Fermentation Temperature: Lower temps need more yeast
Yeast Viability
Liquid Yeast Degradation
Yeast viability decreases over time:
1 month: 80-90% viable
2 months: 60-75% viable
3 months: 40-60% viable
4+ months: Consider a starter
PurePitch® Viability
Formula for White Labs PurePitch® packets:
1 month
99.21%
2 month
98.05%
3 month
90.26%
4 months
84.28%
5 months
79.35%
6 months
71.59%
Dry Yeast
Longer shelf life than liquid
2 years typical viability
10-20 billion cells/gram
No starter needed usually
Making a Yeast Starter
Equipment Needed
Flask: 2L or larger Erlenmeyer
Stir Plate: Optimal for growth
Stir Bar: Magnetic, sanitized
DME: Dry malt extract
Foil: To cover flask
Starter Preparation
Calculate DME Amount
10:1 ratio (100g DME per liter)
Target 1.036-1.040 gravity
Boil and Cool
Boil water and DME 10 minutes
Cool to room temperature
Transfer to sanitized flask
Pitch Yeast
Add yeast to cooled wort
Cover with sanitized foil
Start stir plate
Growth Phase
24-48 hours typical
Keep at room temperature
Constant stirring best
Stepping Up Starters
For very high cell counts:
Make initial 1L starter
After 24-48 hours, add 1L more wort
Continue growth 24 hours
Can repeat for massive counts
Decanting vs. Pitching All
Decanting (Recommended for lagers):
Refrigerate starter overnight
Pour off clear liquid
Pitch concentrated yeast
Pitch Everything (Common for ales):
Add entire starter to wort
Accounts for volume in recipe
Simpler process
Pitch Rate Guidelines
Underpitching Effects
Longer lag time
Stressed yeast
Off-flavors (esters, phenols)
Incomplete fermentation
Diacetyl production
Overpitching Effects
Less yeast character
Reduced esters
Faster fermentation
Possible autolysis
Generally less problematic
Style Considerations
Clean Beers (Lagers, Light Ales):
Higher pitch rates
Minimize yeast stress
Clean fermentation
Character Beers (Belgian, Hefe):
Lower pitch rates acceptable
Encourage ester production
More yeast expression
Dry Yeast Guidelines
Rehydration (Optional)
Boil water, cool to 35-40°C (95-105°F)
Sprinkle yeast on surface
Wait 15 minutes
Gently stir
Pitch when within 5°C (10°F) of wort
Direct Pitch
Modern dry yeast works well
Sprinkle on wort surface
No need to rehydrate
Follow manufacturer guidelines
Amount Needed
Typical: 1 packet per 19 liters (5 gallons) up to 1.060
High Gravity: 2+ packets
Lagers: Double the ale amount
Troubleshooting
Slow Start
Check viability calculation
Verify pitch rate
Consider temperature
Oxygenation levels
Stuck Fermentation
Likely underpitched
Add fresh yeast
Make small starter first
Check temperature
Off-Flavors
Review pitch rate
Check yeast age
Verify storage conditions
Consider yeast health
Using with Your Recipes
Calculate pitch rates based on your recipe's OG and volume
The tool remembers your last settings
Use results to plan yeast purchases and starters
Track what pitch rates work best for your system
Tips
Always calculate pitch rates, don't guess
Use fresh yeast when possible
Keep yeast refrigerated
Aerate wort well before pitching
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