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Yeast Pitch Rate Calculator

Calculate exactly how many yeast cells your batch needs, whether you need a starter, and how to size it.

Under-pitching yeast is the single most common cause of off-flavors in homebrew — this calculator tells you exactly how many cells you need.

The right pitch rate scales with both batch size and gravity: a standard ale wants 0.75 million cells per mL per degree Plato, while a lager needs double that at 1.5 million.

Because liquid yeast loses about 21% viability every month, an older pack may leave you well short — in which case a measured starter grows the cells up before brew day.

1. Pitch Profile

Most ales under 1.060 — pale ale, IPA, amber, brown.

2. Wort Details

Enter 1.030-1.120 as SG, or a value like 12 for Brix/Plato. = 12.4 °P

3. Your Yeast

4 weeks

Viability: 77%

Pitch Analysis

176B

Cells required

77B

Cells available (77% viable)

Starter recommended. You are short ~98B cells. Build a starter or pitch 3 packs.

Without a starter you would need approximately 3 pack(s).

Starter Recipe

1750 mL

Starter volume (1.75 L)

175g

DME (light dry malt extract)

  1. Boil 175g DME in 1750 mL water for 10 minutes (target ~1.040 SG).
  2. Cool to 70°F, pour into a sanitized flask, and pitch your yeast.
  3. Place on a stir plate (or shake often) for 24-36 hours.
  4. Cold-crash, decant the spent wort, and pitch the slurry on brew day.

Estimated yield: ~182B cells.

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💡 Pitch Rate Reference

  • • Standard ale: 0.75M cells/mL/°P
  • • Lager: 1.5M cells/mL/°P (double the ale rate)
  • • High-gravity ale (>1.075): 1.0M cells/mL/°P
  • • Liquid yeast loses ~21% viability per month
  • • Dry yeast: ~20 billion viable cells per gram

Frequently Asked Questions

What is a yeast pitch rate and why does it matter?
Pitch rate is the number of viable yeast cells you add per milliliter of wort, scaled to the wort's sugar content (degrees Plato). Under-pitching forces too few cells to do too much work, producing fusel alcohols, esters, and acetaldehyde. Over-pitching can strip esters and create a thin, characterless beer.
How many cells does a typical 5-gallon ale need?
A standard 5-gallon (19 L) ale at 1.050 OG needs roughly 178 billion cells at the standard ale rate of 0.75M cells/mL/°P. A single fresh 100-billion-cell liquid pack falls short, so a starter or a second pack is recommended.
How does liquid yeast lose viability over time?
Liquid yeast loses roughly 0.7% viability per day, or about 21% per month, from its manufacture date. A pack that was 100 billion cells fresh holds only about 70-80 billion after a month. This calculator applies viability decay based on the pack's age in weeks.
When do I need a yeast starter?
You need a starter whenever your available cell count falls short of the target — common with older liquid yeast, lagers, or high-gravity beers. A starter is a small batch of low-gravity wort (around 1.040) that lets the yeast multiply before pitching. This tool sizes the starter for you.
Is dry yeast different from liquid for pitch rate?
Dry yeast is denser and very stable — about 20 billion viable cells per gram, with high viability for up to two years if stored cool. For many standard-gravity ales, one or two 11g packets sprinkled dry provides enough cells without a starter, making it the simplest option for beginners.

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